If it were me, I would get the HT2-TL, and I would work toward upgrading the amp later. I think that the amp should be selected based upon the speakers' requirements (or you can save up for an Insight Double 440H, and then you can drive anything). While neither the HT2-TL or ST is very demanding, the HT2-TL can handle a lot more power, and with the Insight gear's dynamic range, having some reserve power is a good thing.
The Insight+ SL is a great preamp. When my Insight SL was being upgraded, I was using the pre-out from an old NAD integrated amp. The sound was awful. It didn't matter what DAC or amp that I was using because I wasn't going to get same quality of sound using the NAD pre-out.
1) speakers, 2) preamp, 3) DAC/CDP, and 4) amp (provided that the non-upgraded amp has enough juice to drive the speakers)
Don't forget room treatments, if needed. Don't let anyone tell you that room treatments are snake oil. Frank, IIRC, has a fully treated listening room (the entire ceiling is treated with acoustic materials, and the front wall, at least, is treated with an acoustic "wallpaper").