I have no experience with the Definitions, but like David I have tried numerous examples from virtually every topology--but on my Soul Superflys.
I've tried Firstwatts, Alephs, Class Ds, Class Ts, but what is really standing out and kicking some serious ass is a Redgum Audio RGi120 that I'm borrowing from a friend while my 845 SET is temporarily down.
I almost declined to borrow it as I didn't expect it to fill the void of my Shindo/845 combo, but this little Australian integrated is damn near perfect for my tastes. Sweet, dynamic, clean, liquid and really, really friggin' engaging. I don't know that its completely linear and the bass may be tipped up just a tad, but in a very pleasing, super-engaging way.
Tomorrow I'm taking delivery of a pair of Pavane 845-Ts to bring my monoblocks back to life and once they have broken in I'll have to do some serious a/bing and soul searching to see if I really need more then this Redgum to keep me happy.
Interestingly, the Redgum with its passive volume control doesn't seem to like to be used behind a preamplifier. Its happier alone than driven by my minimax or shindo auregies l.
A distant second in solid state for me were borrowed Pass Alephs driven by a nice tube amp.