Yep, the CP2000 has always been a genuine 2000watts - 1,000 RMS per side into two ohms. I was pretty sure it had speakon outs though.

What you want to do is get an active crossover, like a Behringer Ultracross (they are quite cheap), and a smaller but similar power amp. Then use the small one to drive the tops and teh Yamaha to drive the subs.

Then build some tops - they can be quite small, I have built a useful pair out of two old kitchen cabinets with proper reinforcing, and then put two Motorola Powerline pezo horns and one 10 inch Eminence (I used Kappapro 10s) in them and you'll have a good pair of tops for about £200 all in. THe crossover andthe other amp will be the expensive bit, so you could just put a pair of speakers like this on the top of your existing ones as an interim measure.