You should be able to get more out of your TRUE as the difference in temperature (Delta) between the ambient temp and the TRUE would be considerably higher, which means the volume of air you are shifting would have more of an impact than it currently is - ironically, increasing the heat load might actually make your heatsink more efficient.
The problem is the load calculation. You have to select the TEC carefully. If you choose too small a TEC it will actually end up feeding heat back into the CPU and it'll go from hot to Thermo-nuclear meltdown within milliseconds! Also, if you go beyond the standard 40x40mm size (which happens beyond about 320W) you start to have problems covering all of the surface of the TEC - again, a bad thing.
I'll have a dig around and see if I can find the old load calculator and TEC guide. Worth dropping me an email (in trust) and I'll point you in the direction of some very knowledgeable guys who helped me when I was playing with them.
The stock answer for 'can I use Air-cooling in a TEC rig?' is normally a patronizing laugh, but I think your set up might just be good enough

Well worth a look when you're done with the current play-rig!