Okay, here's a stub for later thoughts, launching with my pre-buy impressions:

Here's the official word:
http://www.behringer.com/EN/Products/BX4500H.aspx

This beast really does it all, & at an official 36 pounds is not as chunky or awkward as I'd feared -- the end-mounted handle (smart move!!) makes it almost easy to sling around.

I've been playing it here-&-there as time allows, & I really need to give it a serious workout, but at practice volumes I'm duly impressed. Retail $501.99 (seriously? from what orifice do companies pull these numbers?), commonly about $250 street & a good deal at that.

http://www.behringer.com/assets...500H_P0362_Front_XXL.jpg
For me, the knobs & buttons run a risk of setting off my OCD. Four up-front on/off pushbuttons: UltraBass, Deep, Bright, Shape -- all four have LEDs lit when engaged. And god bless Behringer: an effects loop. My biggest dislike thus far: separate jacks for passive & active pickups -- the Fender Rumble just has a switch, which allows me to fake a two-channel.

Unlike Fender & other companies, the head is packed with a two-switch floorbox for the UltraBass & Shape functions. And front-routing the jack makes a LOT of sense.

The backlit VU meter looks cool, but actually serves a purpose: hit some hard notes, & set the Gain knob so the peaks tap the needle just a bit into the red, for maximum input without undue distortion. Though not explicit, I figure this is the limiter.

The UltraBass is distinctive: an octave divider. I can get something approximating the sound of the Pearl Jam "Jeremy" intro without needing an 8-string bass. The effect is MUCH more pronounced in the lower tones, but does add a nice little shimmer when playing the G string up around fret 12. With both UB & Deep in play, I get GREAT rich tone at very low volumes.

The Mid control is flanked by knobs that allow setting the width of the mid-notch -- you can knock out the mids to reduce onstage mud, & dial in the tails. Again, props to Behringer for this.

And if you want more snap, whether for funky popping or solos that sing, the Bright switch is great.

Thus far, I can't describe what the Shape knob does, but I like it. I'll get back to you on that.

As I'm running an 8-ohm cabinet, I can't get full power. Looking at the specs, the head seems meant to work best with dual fours.

The front panel XLR is a post-EQ direct input, which means that this head could readily be used as a PA head from a passive mixer board.

All in all, I'm happy with it. On the TalkBass forums, a few snobs say it's not as good as a Genz Benz or similar. Well, yah: at a $500+ street price, a GB had BETTER be better (though at less than stadium-level volumes I'm not convinced). But for $250 or less, the 4500 is a heavy hitter.

These amps are surprizingly GOOD!
Our bassist has 1 + the 4x10 Cabinet with Bugera speakers.

It seriously projects some bass!

Listen here:

http://www.youtube.com/watch?v=19AsfnlJl1A

Overran the recording!

Hi J:
I thought that Bugera is the main line of guitar amps, that is owned by behringer.
Maybe the Bugera is primarily the tube portion of it though.
T

I will admit that I'm a fan of Uli Behringer:
http://ph.linkedin.com/in/ulibehringer
He seems to be following the lead of Ikutaro Kakehashi, the founder of Roland: get as much player input as possible. Put together a beta, hand it off to a gigging pro for a few weeks, then ask what worked & what didn't & what could be added. When the design is set in stone, pretend it's going to be thrown in & out of trucks for a few years, & build the outerware accordingly.

Over the years I've made fun of more than a few companies who seem to get all wrapped up in making better bells-&-whistles toys, which no working musician seems to want. I've played dozens of Fender amps that were overpriced crapboxes, & what was Gibson thinking with the Firebird X?

So, if Behringer puts out something that seems odd or even weird, I might give it a bit more of a chance than I'd offer another company. Not that I'll grit my teeth & give a pass to a "cool" idea gone horribly wrong.

Behringer seems to stick close to its strength -- amplifiers -- with a little stretching to speakers, PA, & stompboxes. In like manner, as much as I've liked a few Gallien-Krueger guitar amps, their core has been solid-state bass amps.

And they DO make some missteps. Having read dozens of reviews, it's clear that the BX4500H is VERY superior to their somewhat cheaper BXR1800H -- the latter seems to burn up readily.

As far as guitar amps, Behringer's strength seems to be with their Ultracoustic combo line & the V-Amp modeler/effects.

Well, we're already drifting from the topic, so whatever...

I keep an eye open for oddities, & in the above context I remembered the Behringer AC112:
http://www.behringer.com/EN/Products/AC112.aspx

Let's just say that it's a small (well, 60 wRMS) combo amp loaded with all sorts of sims & digital effects -- oh, MIDI-controlled besides, & with a 12AX7. I mean, don't it just remind you of one of those grand 1980s Roland experiments??? Have a browse through the manual.

Discontinued, but findable, & not terribly pricey:
http://www.musicgoround.com/detail.aspx?id=1107684

The V-Am Pro rackmount has been showing up used for under $100 as well, so unless you're set on the desktop box it's worth a look.