Do I need to amplify all of my channels?

Your Mac seem to be a bit wimpy in the area of reserves (judging by the specs), so if you want to use it for the surround channels ONLY and you don't crank it up for extended periods you should be okay. Not great, but okay. Your front 3 channels need more power. 3 channels of Mac amplification would fill your bill (look for a Mac amp that double its' power rating into 4 ohms. Example-100 watts into 8 ohms, 200 watts into 4 ohms)

When you do the AVR settings (level, delay) do this at your typical listening level and your levels should be balanced.

Your best, though not least expensive option would be to get a higher power Mac driving all 7 channels.

Alternatively get a high-end 7-channel Marantz amp. For a (mainly) Home Theater rig this is likely about as good a compromise (cost/performance) as you'll get. IMHO.

your very nice B & W's deserve some more power. I would buy a good Mac Amp (MC 2255?) for your 803's and use the PreOuts from your processor. Use the processors power for the center and rear speakers.

Srwooten

Thanks for the thoughts, yes the MHT100 is a bit of a wimp. When it bought it, the MHT was a great compromise for me - excellent quality, but not separates. I knew that I would eventually add an amp and still have a great processor - that time has come. I am leaning toward 7 channels as my room is wired for such and the MHT produces 7.1 if it is offloaded to an amp.

Is there any particular logic related to amps whose power doubles into 4 ohms? Are there particular Marantz models recommended?

Also, I am not opposed to a used amp, in fact, I may go that way - I know there are several bargains (quality versus price depreciation) in older models.

Thanks
Mark

your room and listneing levels should give you an idea on your power needs.... However, generally speaking, having BW about, think of power, as your friend. your best friend.

Certainly speakers need power. BW speakers do well with a lot of it, I've had 5 sets.

I don't feel it necessary to stay 'same - same' with processor & amp either. With speakers, that approach works indeed, across the front 3, with rears & surrounds, mattering much less.

Assuming here you have a processor - AV multi ch preamp, or receiver on hand and further, it has main pre outputs, DEFINITELY adding an amp is IME a necessity with BW.

As to how many channels? you pick. Flavor? Again, that's on you too. Figure EVERY ch in the amp will drive one speaker and the proc will drive the powered sub. Simple.

I'd look for a smooth top end in whichever amp first. Secondly, 200 wpc or so, or in that area. I'd bet the ATI 2505, or one of the newer 1805, or 2005, ATI amps would be a good match.

Another thought too is your note on using your existing gear/space for 2 ch. audio. Perhaps TWO amps would be a better approach. One for center surrounds and rears and one for the main 803s. This would be my choice at some point if not initially. Naturally, for a more cohesive sound field, the optimum fix is same speakers all around, and the same flavor power all about too. ?? Well, it is a goal, but not always done 100%. Truth be told you can do pretty well with some compromises to that theme too.

Try also to minimize other diffs too if a pair of amps is sought out... like interconnects and power cables & speaker wires.

I went your route somewhat but in reverse. Adding a two ch amp first. Then, felt for myself, a multi ch amp would be best and as above, more congruent given my speaks are closely mated all around. My current 5 ch amp however will only drive 3 ch of my system, L, C, & R, WITH the initial SS amp driving my rears in a 5.1 affair.

Why? Two reasons... it has a better sonic thumbprint than the Odyssey Stratos Plus +, and it allows for more coherence in the important area. A third aspect is that with many multi ch amps, and mine in particular, using less of the ch at one time allows for a higher power output across fewer channels.

What about the other two ch of the 5 ch amp? I really am not sure how I'll use them.

Good luck.

If you want to 'wake up' bass in your speakers I suggest to look to power them up in 500w/ch amplification range.
I've got my itchy hands to upgrade to Wyred4sound SX500 monos from BCarver Sunfire SRA(250W/ch) which I also can recommend to you.
BTW if you're interested in Sunfire SRA(which is much better match then your current amp) drop me a note with possible offer(open).