I have my system set up for 2 channel and multi-channel (home theatre).  I recently bought a set of Martin Logan Ethos and a McIntosh MC452.  Most of the listening I do is 2 channel and I like using my powered subwoofer for 2 channel music.  I currently have a Nuforce AVP-17 that I use to pass through the analog from an Oppo BDP-105.  I'm interested in trying another preamp.  I was recently made aware of Decware's Ultra preamp by someone on another forum.  
The flexibility of the Ultra sounds very intriguing!  I've never owned any tube gear.  Has anyone here ever paired a tube preamp with a solid state amplifier?  If so, did you like what you heard?  I often hear of the 'smooth' nature of tubes.  What exactly does that mean?  Is it a rolling off of the upper frequencies?

Kurt, I started with all solid state setup including a McIntosh preamp and amp.  I wanted to add a tube preamp to make the sound more organic.  It did and I was able to tailor the sound by trying different tubes.  I highly recommend putting tubes somewhere in the chain.  I was hooked enough to drive the rest of the way to all tubes today with a Cary SLP98P preamp mated to a Decware ZMA amp.  I love this combination.  The Decware Ultra preamp looks like a very flexible solution if you are juggling multiple channels.

One reality of mixing a tube preamp with a SS amp is that care should be taken with impedance to ensure the frequency curve doesn't roll off audibly at low and high extremes.  A general rule of thumb is that the output impedance of the preamp should be at least 10 to 20 times less than the input impedance of the amp.  You probably won't have any issue, but Mac amps all have somewhat lower input impedance ratings, which suggests you want to aim at preamps with lower output impedances to compensate.  Your MC452 is rated at 22k ohms.

Give Steve a call and talk to him about your Mac amp.  He likely is familiar with their specs and can comment on this matching issue.  Tube amps, just as a point of comparison, all have input impedances of at least 100k ohms, some as high as 200k ohms.  Any preamp will work with a tube amp.