I would choose a valve body upgrade (Especially a Level 10 Valve Body upgrade) over the small car shift kit. There IS a performance improvement with the shift kit. Trust me! On my Outback Sport, torque between shifts went up to 50% more than my normal output. Shifts are REALLY firm to harsh. When I requested this at the Level 10 shop, they (Pat-the owner, and the mechanic) both laughed at me and the mechanic said, "Don't worry, it'll be nice and firm". I couldn't be happier. It is NOT for everyone though. It may be too firm shifting for some. It can actually snap the steering wheel left or right between shifts if you are not careful. No matter how much abuse I threw at the OBS afterwards, the tranny still ran and still runs much stronger than it did stock. The BIG downside to having a valvebody upgrade done at Level10 is the cost. From what I remember, it was between $1200-$1300 ($700 for valvebody and approx $500 labor). I got raped for the labor since I waited 8 hours for it to get done. Pat Barret (I believe that is his name..he's the owner of Level10) showed me around the shop and kinda taught me what they did with the insides of the trannys. He had various trannys out and apart of Hondas, Mitsus, etc and was showing what gets done on a tranny rebuild and valvebody. He also showed me his photo albums of the shops and people he does work for (and train) over in the Middle East. There was a shiek or two arriving that day but I was not around long enough to meet them. With the class teaching and personal attention, I shrugged off the extra cost of labor.
On another front, for those that do not have a bad tranny, talk to a tranny shop to see if they can upgrade your valve body. I talked to a shop here in Delaware (Claymont) called Benchmark Transmission. The shop's owner is Michael Neubaur (sp?) and he talks and talks and talks. Shows what gets done the the valvebody with and upgrade and likes to talk about the ins and outs of transmissions. He upgraded both of my valvebodys in both of my autotranny XT6s (FWD and AWD). My 2nd-3rd gears aren't as strong as my Level 10 valvebody but they are much better than stock and better than if I unplugged my tranny resistor to have the affect of the Small Car shiftkit.
And from what I remember, the valvebody job at the tranny shop cost between $200-$300. Very affordable and doable. Call your tranny shop to inquire about this. You may be pleasantly surprised if they guys can be trusted and they know transmissions.
I am considering a valvebody upgrade on my SVX despite it being 4.44 with a small car shiftkit. The shifts between gears isn't quick enough and I have this aching feeling something bad is going to happen. Maybe that is because before upgrading my scoobies, both my XT6s and my Outback Sport had a tranny that failed.
Lots of $$$ and a learning experience. I have no doubt that those trannys will last a LONG time now no matter what. I want the same for my SVX.
So, a regular tranny with a valvebody upgrade and tranny cooler installed. That is all I think you will need.