one 7 channel amp or seperate 2 channel amps?

Why not biamp? the Titan sounds like a nice unit. Run four amps of it to the speakers (you'll need to biwire them). that should knock your socks off, and likely you'll feel no need to purchase a new amp for main speakers. The only drawback, then you'll be looking for an amp for two of your surround channels.
Some suggest you must match all amps in your system. If that's not critical to you, then you can experiment with many options for surround amps, and can possibly purchase one of less cost than a dedicated two channel for mains.
Just a thought. Purists might frown on this suggestion, but I'm brainstorming. I have biamped, and found it to reveal a whole new level of listening enjoyment.

I have been all over this same issue in the past 3 years - 2 amps, 1 amp and 4 amps to run 5 channels! This is not an easy decision....

To run a Talon "Raven's Nest" 5.1 setup, I started with a 2-channel Pass Labs X-250 and 3-channel X-3. Though the sonic synergy with the Talons wasn't really there, the dynamics WERE terrific.

Next, and like Mr. Pixel above, I then employed a Titan running all 5 channels for the same speakers, and it was really great. It matched the Talons' sonic characteristics perfectly - smooth and natural, it's amazingly cool-running (efficient), provided a very deep image/stage, never sounded stressed even in *HEAVY* 5.1 use and was just plain easy to live with. I didn't realize just how good this amp was until I sold it...

Then, in my infinite wisdom, I surmised that 3 monoblocks for L/C/R and another running stereo for the rears *MUST* be better for dynamics and overall sonics then one good 5-chnl amp. To be honest however, I really gained nothing decernable except system complication - just more expensive cables, more rack space taken up, etc. And these mono amps are no slouch (Electrocompaniet AW220's).

Having said all this, I am now going to try to get back to a simpler middle-ground. I have a 2-channel Sim W-5 LE on order right now, intending to replace a pair of the monos to drive the front channels and use exclusively for 2-channel operation. If this works out well, I may jump on a 3-channel Titan to drive the rest of the setup (center & rears).

Keep in mind that ALL of my equipment has always run from ONE 20-amp AC outlet, feeding a single B-P-T 3.5 Signature line conditioner to drive all the stuff - including all the amps. I know this is not optimal, and could certainly effect the results here, but I can't add dedicated circuits to my environment right now. At least the power conditions have remained identical throughout these changes in amps.

I don't know if this will help in your decision, but I CAN tell you that the Titan has never sounded like an amp "compromised" by running all 5 channels in my system.

..... But YMMV .....
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I prefer using multiple amps. I use one amp to power the main speakers which I use for movies and 2 channel listening. I have a stereo surround amp in the back of the room, so I use long shielded RCAs and shorter speaker wires. I also use a third amp to power two center channel speakers, one on each side of the TV monitor.
Sonny

Pr: Never seen a multi-channel amp with multiple AC cords. Sounds like a well designed amp. I can understand why you're happy with it if the rest of the design is up to that level. Sean
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BTW - Only using 5 channels.

The amp has two power cords. Also, I have a dedicated a/c feed.

Later,

Pr: Think of how much current is being drawn through that one power cord at any given time feeding 7 channels simultaneously. If going that route, a heavy gauge conductor and a dedicated 20+ amp feed is a must. That is, if you really want the amp to be able to do what it can. Sean
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The Titan is one hell of an amp for home theater. At one time I had 5 amps in my H/T rig. Got rid of them all and purchased a 7 channel amp (7 monoblocks in a single chasis) and have not looked back. Think of all the money you'll save on power cords.

I'm using a 2 channel for my HT mains and a 5 channel for the center, surrounds and two subs. My experience is that most multi-channel amps aren't quite as good as a solid 2 channel amp, so i went this route. Depending on the quality of the multi-channel amp and the amount of performance that you want out of your system, it can go either way. The less demanding of a load that your speakers are, the more likely that a high grade multi-channel amp will be satisfactory. Obviously, how much you listen to 2 channel through this system may also influence your decision. Sean
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I personally am using a 2 channel amp for my two mains and a 5 channel amp for my center and surrounds. I still listen to stereo music occasionally and having a high end 2 channel amp helps out!

Depends on budget, and space, If it were me I would want as much independence as possible so if something needs to be tweaked later you have more options with seperates, but you need the space to put them in also....go with your gut.