Hi and welcome aboard!
I liked the fact that the SPT exhaust was $349 (I think you can still find some discounted ones if you dig around). I went w/ Cobb though because I believe it will be a little louder- the SPT is quiet, too quiet for my likes. Don't get me wrong I don't like loud, but the Cobb exhausts have a reputation of being like Goldilocks- just right I think the Cobb unit is more open as well, likely to net a few extra ponies. The welds/finish on the Cobb is pretty impressive, I've had a lot of high end exhausts in the past and I'd have to say the Cobb is right at the top in that category- hopefully fit is as well
Don't have the Cosworth filter installed yet, my guess any gains will be small, but even small gains will be welcome.
I'm hoping for some dyno time in the near future- I want to get a base run or two and then put the exhaust/filter on and get a couple more- not expecting miracles from a cat-back and a panel filter, but would guess a small bump up (SPT reported a ~10hp gain w/ there catback)