I would also like to see AMD based $625 system in the next build, Core 2 Duo E8X00 for the $1250 and the i7 920 or 940 for the $2500 system. (For reference, my system history has been Intel Pent 1, Amd Athlon Thunderbird, Intel Pent 4 Prescott Socket 478, then Intel Core 2 Duo.) So, I'm not a "fanboy," but would like to see how the new Phenom compares.
Drop the SSDs and try a software Raid 1 + 0 using high quality 7.2k drives with sufficient capacity for the $2500 system. (No hardware raid cost, performance of a Raid 0, redundancy of a Raid 1, using ~640 or 750 GB drives.)
Use Amd graphics with Intel processors and Nvidia graphics with Amd processors, per your own performance reviews that showed these setups as the best for a majority of games.
Use 6 GB of ram instead of 12 in the $2500 system, and stick with 4 GB in the other two.
Drop water cooling all together, and stick with cases, cpu coolers, and graphics cards known for their cooling capability. (Meaning, no reference coolers on video cards.) Most builders don't watercool.
Include duel drives in the total cost of the 2 higher priced systems. (Bluray and DVD burner for the $2500, duel DVD burners for the $1250) Most people put duel burners in machines these days due to the low cost and added "protection" in the event a drive fails.
Crossfire the $1250 system's graphics. (More immediate graphics "bang for buck" with two cheaper cards than one expensive one.)
Forget secondary sound cards in all systems. Pick up MBs that have good onboard sound.
On the $625 and maybe the $1250 system, pick MBs (if possible) that still have at least a single IDE channel. This would allow a user to put their old hard drive in the system as extra storage in an upgrade scenario.
The above is just my personal preferences, as we all have them. Thank you for listening to people's comments and using parts (IE: testing) that may or may not provide the edge we are looking for.