I'll be adding this drive to this motherboard. I realize I won't get Sata III benefits and that I don't have AHCI support. Are there any other issues I should be aware of or anything I can do to improve my situation, aside from a complete overhaul?
More about :sandisk extreme ssd 120gb asus p5n mobo
Modern SSDs use idle Garbage Collection in addition to TRIM to maintain drive performance.
Since your SSD will be in IDE mode TRIM will probably not be enabled so just Log off (not Shut down) overnight while you sleep once or twice a week to allow GC to do its thing.
In Control Panel go to Power Options and set your SSD to Never shut down so that it doesn't go to sleep while your system is logged off.