As far as sticking with one amp, although I dont fully understand the purpose of it - quality is quality - I'll try and help you out.
First off, if you want to run the same brand amp for everything, don't get Rockford. Second of all, you dont NEED 1000 watts per subwoofer, 700 per sub would be more than enough. Now onto the good stuff, here are a couple setups you could go with (keep in mind all amps listed for subs, you will need 2 for them unless specified otherwise):
Number one - Phoenix Gold
Amps for subs - Phoenix Gold 1200.1 -
http://www.sounddomain.com/sku/PHOT12001 . This pushes 1200 watts from a 2 ohm load, meaning you could get about 800-900 watts per subwoofer with a 3 ohm load.
Amp for speakers - 4 channel - Phoenix Gold Tantrum 600.4 -
http://www.sounddomain.com/sku/PHOT6004
Amp for speakers - 2 channel - Phoenix Gold Tantrum 250.2 -
http://www.sounddomain.com/sku/PHOT2502
Number two - MTX
Amps for subs - MTX Thunder 8100D -
http://www.sounddomain.com/sku/MTX81000D . This pushes 1500 watts from a 2 ohm load, meaning you could get around 1000 watts per subwoofer with a 3 ohm load.
Amp for speakers - 4 channel - MTX Thunder 4244 -
http://www.sounddomain.com/sku/MTX4244
Amp for speakers - 2 channel - MTX Thunder 4202 -
http://www.sounddomain.com/sku/MTX4202
Number three - JBL
Amps for subs - JBL 1200.1 -
http://www.etronics.com/product.asp?stk_code=jblbp12001 . This pushes 1200 watts into a 2 ohm load, so youd get 800-900 watts per subwoofer with a 3 ohm load.
Amp for speakers - 4 channel - JBL 80.4 -
http://www.etronics.com/product.asp?stk_code=jblp804
Amp for speakers - 2 channel - JBL 180.2 -
http://www.etronics.com/product.asp?stk_code=jblp1802
Number four - Soundstream
Amps for subs - SoundStream Picasso 1400.1D -
http://www.etronics.com/product.asp?stk_code=soupic11400d - This pushes 700 watts from a 2 ohm load, so youd get about 900-1000 watts per subwoofer with a 3 ohm load.
Amp for speakers - 4 channel - SoundStream Picasso 640.4 -
http://www.etronics.com/product.asp?stk_code=soupic4640
Amp for speakers - 2 channel - SoundStream Picasso 320.2 -
http://www.etronics.com/product.asp?stk_code=soupic2320
There are some other options out there, but I dont feel like looking around for all of them. But if you were to go with one of these setups, I would not hesitate to say go with SoundStream. They make some of the most efficient and reliable amps on the market today, and the price is very reasonable. After SoundStream i'd go with Phoenix Gold. MTX and JBL are a slight notch below these 2 brands.
As far as the placement of speakers, number one do not add speakers to the subwoofer box. I myself dont worry about rear fill too much, i'm sitting in the front so I could give two shits about whats going on in the back as long as its decent. What you have right now should be way more than enough to satisfy your needs.