Generation IV External Engine - Ported LS2 head enough?

2005 GTO with stock heads, SW LT's, Magnaflow and a bumpstick
measuring 235/241 .614 on 112. I am looking to just get a quality port
and valve job on the stock heads. I am looking for opinions on how much I am leaving on the table not going aftermarket with the heads.

If the port and valve job is good you will be leaving very little on the table...you may even make a little more than the aftermarket head in as shipped form.

I would send them to TEA and you're good.

http://www.totalengineairflow.com/products/gmhead/gmls6/

Well I did not have the coin to do the aftermarket heads along with the other upgrades I had decided on. My cam is a Flowtech grind and I have been very happy with it so I decided to have Flowtech do the heads also. As the heads go back on I have bought a few other pieces to go on also. I am shooting for 400 to the wheels uncorrected.

Flowtech CNC ported, combustion chamber, blending of runners and bowl
Serdi Valve job
PAC Racing 1521 with my comp 921 Ti retainers
Comp Cams Ultra Pro-Magnum LSx rocker kit
FAST 102
Vararam