It just depends what your goals are, and how much you're willing to spend. You have a decent start for some power, but it doesn't come cheap. The flex fuel engines have a slightly higher stock compression ratio, and running e-85 can have nice benefits too. Especially for forced induction. As far as specific upgrades go,
IMO, there are 3 stages of engine mods for the 3.0.
Stage 1: ( Simple bolt-ons, fairly inexpensive, will improve throttle response, slight increases in power, and can improve mileage)
underdrive pulleys
a decent cat-back exhaust
electric fan
Air intake kit
*an sct X-cal tuner
Stage 2: (More indepth install requirements, increased cost, work best in conjunction with Stage 1 mods)
porting/polishing heads and intakes
roller rockers
headers
*an sct X-cal tuner
Stage 3 : (Most advanced, will see largest power gains, highest cost, )
Tom Morana products
Forced induction
*an sct X-cal tuner
*The tuner can be done at any stage, but making the tuner the last mod you do will allow the tunes to account for other mods, and therefore have a larger net affect on performance. It also keeps you from spending money on additional tunes if you mod things after purchasing the tuner.