New Amp Choice

I am not sure what is left for a tangible improvement, but I am looking at trying at least one additional amp. I stared with high end receivers, but then bough a McIntosh MA7900 nearly 4 years ago along with Golden Ear Triton Ones. I find the the sound quite good though I had a low end Pioneer receiver once with some surround type Bose speakers, hisses noted, and they had a quality off whipping the sound while moving around me that I really liked. My current system which I described, is much cleaner and detailed, but there was an enveloping aspect that I still miss. Maybe a new amp will not supply any of this as it is a quality of the speaker, but I wondered if a tube amp has such a quality. I may purchase a pair of Bose 301's just to test, but I am still minded to try another higher end amp and to be clear while I likded that aspect of the Bose my current setup is in most regards more pleasing.

The contenders are:

Pass Labs Int-250
Musical Fidelity M8xi
Line Magnetic  LM-845IA   
Line Magnetic LM-845 Premium

The Luxman 509x was of interest, but they gimped the headphone output.