Get Polk speakers and a clean sweep. Alpine has fantastic sound quality for their amps. Kenwood is ****, infinity is over rated IMO...clean but so flat and lacks midbass.
Also, if yo are serious about adding a sub down the road run at least 4 guage power and grounds with a distribution block so you can simply plug and play when you add another amp down the road. You may spend a BIT more today, but you will save a lot of time and money in the future when you complete the system. Depending on how you like to wire your system you may want to run a second set of RCAs, although personally I prefer to daisy chain and double up on the crossover/filters.
2005 White Lariat 5.4 Supercrew
Roush Stage 2 Conversion
2/5 Drop, Air Shocks, Branzach BZ-11 22s, Nitto A420 305/40/22s. Magnaflow catback. GREEN Coldair Intake. Troyer Tuned Xcal2, Re-geared 4.1 LS, Line-X, Window Tint, Mark LT Handles, White Tailgate Oval, Roush Stage 2 Badges, Upper/Lower Polished Carriage Works Grills, Roush Front Spoiler, JL Cleansweep, JL 500/1, JL 450/4, JL Stealthbox, Polk MOMO 6.5 seperates Front, MOMO 5x7s Rear, 100 FT Dynamat Xtreme, Xm Commander.