Looking for a new amp

[Corsa-Craig]

im planning an upgrade to my ice install very soon, the existing install consists of a 1000w peak (250rms) jbl 12" sub and 400w (250/60w rms) JBL Amp. Im looking to buy 2x 10" 1000w (250w rms) jbl subs to add alongside the 12". Would I be better off running the existing sub off the existing amp and getting a new amp to power the 2 10" subs, or running the lot off 1 new amp. If so could anyone point me in the direction of a cheap(ish) amp which would have enough power to run all of the subs. This is my first install so when it comes to amps I dont really know what im looking for. Im guessing that this option would mean gettin a 4 channel amp with at least 750w rms power? Also guessin I'll need a power cap or two aswell

Thanks for any help
Craig