I've owned the ST-140, warm. I had it paired with an Adcom GFP-565, and I wouldn't characterize the Adcom as warm. Depending on cabling, I'd call it a bit lean-to-neutral sounding. You should have a complementary pairing there.
I second the recommendation of the Kestrel's. If you have to go with monitors, the Vienna Hayden's would work nicely.
I second the recommendation of the Kestrel's. If you have to go with monitors, the Vienna Hayden's would work nicely.