Let me ask you a question first - What is it that you are looking to improve? Better 2-channel performance? "Louder" Home Theater sound? etc....
For reference, I own Talon Raven C's, a Falcon C center chnl, Martin Logan Stylos (on-wall) rears and a REL Stadium III sub. I also use both a VAC tube preamp -AND- an EAD TheaterMaster pre/pro simultaneously.
This gives me a "dedicated" 2-channel system when I want 'pure' tube stereo performance, while still being able to fully integrate the other 3 amplified channels and sub for HT using the pre/pro and the VAC's Cinema Bypass input. Yes - there is alot of components involved. Lots of cables, intercons, rack space, etc. I guess I manage to justify it all through the system's extreme versatility...
However, I used to have a Titan 5, that powered all channels except the sub. I was VERY happy with it's sound, build-quality and easy-going nature in all conditions. Plus, it is VERY synergistic with Talon speakers. But that did not stop me from asking the same question you are - "Would multiple amps sound alot BETTER then this single 5-channel multichamp?".
So, I first swapped it for an all-monoblock setup (Electrocompaniet's). Now that is gone and I feel that I have found a nice compromise in a Sim Audio W-5LE for the mains and a Titan 3-channel for the rest.
Admittedly, the system has changed alot since the Titan 5 was there, but I am quite certain that the W-5LE is a "better" amp then the Titan for stunning 2-channel performance with Talons. It is a more detailed, impactful and cleaner sound - more mature yet dynamic. The headroom is awesome - it never runs out of steam or seems strained. Basically, take all the things that you like about the Titan and multiply it by 150%.
-BUT- having said all that, the Titan STILL ain't no slouch by itself. I could EASILY go back to a Titan 5 and be quite content.
So, the moral of the story is - if you prize ultimate 2-channel performance, have enough space, power, intercons and Money to justify another amp, you may want to consider adding a separate 2-channel amp to act as a companion to your Titan. The Titan can always run the rest of the channels just fine, allowing you to experiment with different stereo amps to your heart's content. And if this addition does not turn out to justify itself, then you can sell the 2-chnl amp and go back to the T-7 alone - no harm, no foul.
Hope that helps...