Front and rear amps

I am ugrading my "stereo" to home theater after many years. I have an old B&K ST-202 modified by Sound Unlimited along with a B&K MC Sonata 10 preamp. I realize I will have to upgrade the preamp to a new preamp/processor. I am wondering if I have options with the amp. Can I use it for the rear channels and get a new 3 channel amp for the fronts and center. Do they need to be from B&K or can I get something else. Or should I just get a new 5 channel amp. I'm still auditioning speakers but I am leaning towards Magnepans. Any thoughts would be appreciated.
Sure you can use them for rear channels. It has been my experience that rear channel amplification does not matter a whole heck of a lot. I have had very expensive amps (and great sounding) amplifying my rear channels, and I could not tell the difference between them and a SOny 5*100wpc solid state amp.

Going with Maggies, I would think power as far as amplification goes. There are several threads here about powerin Maggie 3.6s.

Anyway, I have owned Maggie 3.6s, and I am not convinced that they are a good choice at all for home theater applications when compared to a nice dynamic box speaker. Maggie speakers in general are just not that dynamic. People who say they are... well... have not compared them side by side to nice box speakers.

I run my HT system through my 2 channel setup. Look at my system here at Audiogon and you might get some ideas.

I agree with KF about the rear amps -- they are not nearly as critical as the amp driving your front speakers. It is not necessary to buy a new 5-channel HT amp unless you have a desire for a serious upgrade. If you use your 2-channel amp for the rear, you will (obviously) need a 3-channel amp for the left, center, and right speakers (assuming you're planning a 5.1, rather than 6.1 or 7.1, surround system). This 3-channel amp should be of good quality to drive the Maggies you are considering. Ideally, your center speaker should be a Maggie, since the center channel should have very similar sound quality to the main speakers (this is particularly true with Maggies which have a distinctive sound).

With regard to power, I have found that in most home theater systems, 100 watts per channel is more than enough for the rear channel speakers, unless you running large, full-range rear speakers. The Maggies, however, really need more power than that (I think 200 wpc is about the minimum), particularly if you will be using them for music played at moderately high volume levels. Maggies are a bit difficult to drive, so you should do some research in the Audiogon archives for threads about amps that are best suited to Maggies.
Thanks for the input. I'm still looking for speakers and haven't made my decision. I listen to music most of the time and I like the Magnepans for that (I'm looking at the 1.6 by the way). I think I'll be fine with the B&Ks in the rear. Any suggestions for a three channel front amp. I'm considering B&K, Bryston, Anthem and a few others in the 100-200W range. I'd consider Krell or McIntosh if I can find a used one for less than $2,000. I've heard that some of the older McIntosh which would fit my price range aren't that good.
I just finished breaking in an Anthem MCA 30 that I'm using to drive my LFC speakers. It's mated with a Classe SSP 30 and it sounds wonderful for Home theatre and 2 channel. If money is an object(and it generally is) then value for dollar the Anthem is a great buy for thousands less than the B&K and Bryston.
I am partial to Aragon, I had a similar situation with Maggies and an Aragon 2 channel amp. I almost changed to a conventional box speaker and then found Martin Logans to be a great compromise. I kept the 2 channel 4004 and added the 3 channel 8008x3 that gives me 200 each channel. I would keep the B&K and look for a used 8008, it will drive anything. Martin Logans are great if you have the room to place them a couple of feet of the wall, and you have a wife as understanding as mine. Once you get them in the theater watching movies with the kids they really do not care what they look like if you have room, and if you are considering Maggies you must have room.

I have a Meridian 561 processor that I have been very happy with, but am considering Aragon Soundstage Ultra One. Anyone reading this have any experience with these side by side?