I'm thinking it really depends on what your reason for making mods is. For instance, I love the looks of my 1LT/RS so I'm not spending $$$ on asthetics.
The sound needs some help and I'd like to get max MPGs, so I've ordered MRT-V2 Axleback exhaust and CAI Cold Air Induction. Both are said to increase HP and MPG.
My other concern is keeping my inner engine clean and efficient so, I have ordered an RX Catch Can as well.
So as I said, I think YOU have to pick your priorities once you've put a few miles on it. If I could make only one mod, I'd probably choose the Catch Can. I know the engines are designed to function just fine without it, but I plan on having this car a lonnnnnnnng time. Dirty engine = not good.