USB Help !?

No m8 it's not. You have FOUR 4ohm cabs? Each cab has two 1k drivers, ergo 2000w. The amp you mention will run two of the cabs with much headroom @ 2400w. PERSONALLY I don't think the Celestions will take 1k each, others may know better, so maybe driving each cab with 1.5k would suffice? There are those who hate under driving and those who don't. The USB can be a little brutal on drivers (Ask True Audio Systems on SP), so giving each of those Celestions 750 w MAY be right.
Anyhow, unless you can find an amp that does 4k at 2ohms per channel, and you have the mains to drive it you will still be needing two amps. IE. One cab which is 4 ohms per channel.
Now as you say you have found the FFA, and that is just about the only thing that will do the job, but at 2ohms per channel, not 4 as you stated. Void Inf 8 mk2 the other, plus Camco etc. The FFA 8 will do 4k per chanel at 2ohms, this is what you need. two 4ohm bins a side off this = 2 ohms. It also has the advantage of two 10a mains inputs I think, which theoretically means you wont be neading a 16a plus supply. I would show this thread to Noise Control, let them help you. Bit different from your 500 quid though:)

My suggestion was based on the following:

He only has £5-600 to spend on amps. For that money, you cannot buy amplifiers to drive 2kW/cab, it's just not going to happen. The answer IMO is to give them as much power as you can. Just because a driver is rated at 1kW for example, doesn't mean that you have to give it that much power. Going from say 500W to 1kW will not give you 3dB more because power compression will set in. You might well hit excursion limitations too.

A Berry EP4000 for example is rated at 1400W@4R per channel. I'm willing to believe that it will deliver that, albeit not continuously but few music styles require that. Therefore each driver will get 700WRMS at full power. That is more than enough to get all but the least efficient drivers moving.

Yes it would be nice to get a pair of Camco Vortex 6's, Lab Gruppen fP6400's, Void Infinite 8's and the list goes on but they're not in the budget and also probably unnecessary.

The Behringer amps are just an example but something along those lines is I think realistically what we're looking at here.

Far too much is made of powering cabs with massive amounts of power. For example, I run a Crest 8001 rated at 1200W@4R into two or three 18" reflex cabs. Flat out, each one is getting no more than 500W but it's still rare for me to need to use all of the power available, even doing gigs where the rig looks too small.

Chris I agree with all that you say, in priciple. I did a similar thing with 8r bridged Matrix UKP 1300's for a whule, one per cab.
We'll have to agree to disagree on the Berry subject.
Regards
to all

I'm not saying the Behringers are great amps, however it is hard to avoid the fact that you do get a decent number of Watts for your pound and they are available new with a warranty. And if you don't abuse them, I haven't seen any go wrong.

But anyway.....

Its still an interesting topic how much actual power to allow for drivers. Most of my work 90%+ is live duty and I find that the amplifier requirements for this are totally different than for recorded music.

For instance my little twin 400w 8" mid-tops get stuck on the end of a 1200 watt amplifier and are perfectly happy being run all night with the clip light occasionally flashing. Stick some recorded heavy rock on them and they get to sound a bit stressed as soon as the -10db light starts to come on.

I agree that for some duties the requirement of 1.5x rms for bass is often not needed.

I started with the Berry EP2500's when I got back into live sound and for the money ( I paid £155 brand new for my last one) could not fault them. I also stuck a few into install's and even got quite a few for my mates in bands and they all still talk to me. Good budget workhorse, no more no less.

Tony