You can go ahead and upgrade the ct26 if you really want to. I have had both turbos, an upgraded ct26 and a ct20b. Upgraded ct26 does not come anywhere near the ct20b in performance. An upgraded ct26 will definetly warrent you about 20-30 more hp over a stock ct26, but will also warrent you hotter charge temps. The stock intercooler will not suffice if you decide to race it. To me, the ct20b seems to run more efficiently. Performance wise, the upgraded ct26 made power up until about 5500 rpm then drastically starts dropping off. When I drag raced it, I basically shifted at 6k rpm because anything after that was basically useless. I can take the ct20b to redline in 1st and 2nd, 3rd gear i can take it up to 6500. The ct20b also spools up faster. Now you are going to pay more for a ct20b, but it's well worth the money in my opinion. Plus you can then sell your stocker for about $100-125 to even out the price some, and have no down time. An upgraded ct26 will get you around 225-230rwhp, not much more, the ct20b will get you around 245rwhp. This is typical for cars with basic bolt ons, such as exhaust, intake, ebc, and dp.

Now on the intercooler, if you want to save money, instead of wasteing it on a stupid eclipse intercooler, invest in a good water/alc injection system. They cost less then $300, and are highly effective. I think water/alc injection would be more effective then a greddy sidemount.