Opinion needed: Pre-Amp (bypass a dac)?

[jdcarlson]

For a cheap solution that will also generate 5.1 surround, try the MAC-3. There are newer and better DACs around, but one can pick up a MAC-3 for $500 or so on the used market.
As to using the 150 or 151, while these have room perfect (on all channels) they have no provision for bi-amping speakers. If you anticipate doing that, you will need the MEN220, since it includes provision for bi-amping. BUT - MEN220 is strictly two channel.
I am not familiar with all input options on your current front end gear, but if you go with the MAC-3 you will need some way to handle 5.1 inputs to get surround sound - which is going to require additional power amps and speakers.
Another option is the MHT200. Digital and analog inputs, 7.1 built in, with power amps built in. All in one unit. The big drawback to the MHT200 is that is has no output transformers ("autoformers" per McIntosh) on the power amps.
But - for pure quality of sound, I echo the recommendation for C1000T.
But when you want 5.1 or 7.1 surround sound to have the sound quality of the C1000T, or something similar, along with your MC501s, you are talking about megabucks.