Building a system around Thiel 1.5

If I had those speakers, I would try the Electrocompaniet ECI-3, to warm them up a bit, while keeping the resolution.

I found my Thiel 1.5s did their best with a tube preamp, and solid state amp I had an Anthem. Or you could just try an integrated hybrid such as the Jolida 1501A.

I have Thiel 1.5s as my rear HT speakers. Occasionally, I'll move them to the front where they are driven by my Adcom MOSFET preamp and amp. The amp is 200W/channel at 8 ohms, 350W/channel at 4 ohms. The speakers really have a great sound: musical and good "boogie" factor....add a subwoofer to get the lower frequencies and it should sound really nice.

Er, you're going to have to tinker with this one, just like every other audiphile tweek has had to!
I've had 1.5's and 2.3's over the years, among others. I think you're going to need some "tube" somewhere in the system to help with the foreward mid-trebble reigion. But, cabling will effect as well. Still, if you're going to use solid state, I like tube pre with it(with the right tubes of course). Otherwise, maybe some tube amp with 6550's for bass and snap.
A strong integrated tube amp sounds good if it's powerful enough to push that 4 ohm speaker, that sometimes dips bellow that in certain spots, even though it's bass limited to 40hz reigion.
That said, get a good tube pre, and good SS to consider are Pass X150, Threshold T200, Coda 11(?), and similiar.
Good luck