This is what I did before getting tuned. I had a intake, hot pipe, mac ebcs, xforce exhuast, msd coil packs, then tork motorsports intercooler. At that point I felt the intercooler maybe helped the most with the power in mid to high rpm range. Then I got SXTH Element stage 2 tune which I feel was the best improvement. Then I installed a xforce downpipe after being tuned and only felt there was a minor change in the powerband. So... having said that I think a tune would be the best improvement but a intercooler would help even more along side it,
You certainly don't "Need" one. Your car will be fine without a tune. Mine is in the same boat and it feels just the same without a tune, barring the great sound. Maybe a bit more power and throttle response.
Will you want a tune to help those mods? Probably. It'll make a huge difference in power, the actual power band itself, and even more sound with pops and gurgles, if you want them.
I will be tuning my car eventually, but before I do want to make sure to buy an EBCS.