Power Amplifier conundrum.

I have an old Nikko seperates system Alpha II power amp, gamma 1 tuner, beta II preamp, and EQ1 equalizer. I also have an old Nikko turntable, and a newer Cambridge Audio 540C cd player. Speakers are Klipsch KG4 w/ a DCM 10 subwoofer.
I recently aquired a set of Tannoy Reveal monitors an a 2nd DCM 10 subwoofer.
Here is my question/problem: I have a 2 room office /studio and want to hook up the Tannoy-DCM in the one area and the Klipsch-DCM in the other. I hooked all but the 2nd dcm sub up and after a short while the left channel became scratchy.Turning off 1 set of the speakers and it stopped.( I have an adcom 4 speaker selector switch) I pulled out the amp brochure and there are warnings about running mixed ohm speakers.
I would like to be able to run the system in both areas, and also only in one area or the other as need be. The Beta II will allow the hookup of a second amp if desired so:
1. Could I source another Alpha II and run the second set of speakers off that?
2. Should I consider upgrading the amp? If so what Brand and model would you recommend to carry this load without amp damage?
3. Should I consider a 3 or 5 channel amp? If so what brand and type would you recommend?
The kicker also is budget. I have 2 in college and would like to keep it under $500 if possible.

Thank you in advance for your thoughts and suggestions.
Could it be the Adcom?
I don't know how your amp will get along with the combination of speakers/switcher,but it does sound like the Adcom could be the culprit to me too.With everything shut off,cycle the Adcom switches several times.This may help some.A contact cleaner, even some from Radio Shack sprayed on the contacts in the Adcom could help.To see if it is an amp problem,switch the speaker left and right inputs(from the amp)only at the Adcom switcher.No other changes. If the scratchy sound still comes out of the left speaker,its the switch most likely causing the problem.
The Beta II will allow the hookup of a second amp if desired so:
You could probably get a RCA Y-connector to run two amps from the preamp.I can't remember doing it myself,but a lot of people do it all the time.It may,or may not affect the sound some.Another possibility with your limited budget, would be to run a integrated amp off of the Y connector going to an auxiliary input(on integrated)to help match volume levels. This will degrade the sound some,because there will be a second preamp involved.It still may sound good enough for an office though.Doing this,start at low volume levels at first to be safe,until you find out loudness difference of the amps.Y-connect link.
Any thoughts on a multi channel amp?
A 5 channel amp should work.A lot of home theater oriented amps are 8 ohms,the standard for home theater.At least they do have a fair amount of multi-channel power amps that could still drive 4 ohms.Receivers are getting more oriented toward the 8 ohm,low current.If you find one that sounds good to you,in your price range, I can't see anything against it.It will save shelf space.I can't recommend any on experience,for sound quality,or reliability.I use 3 stereo amps for multichannel,mainly because I already had 2 to start with.Others may have recomendations on what is out there,and how they sound.I can't remember what you Nikko sounded like.I would imagine
you want the new one to sound as good.One more possible plus for a multichannel,would be finding a newer one,just in case yours is getting ready for new caps.Only time would answer that one though.I hope you find something that works for you.
You should just buy the $325 threshold amp for sale right now (10/26/2010) as it will be an elevator ride over where you are currently sitting with your amp IMHO. I have no affiliation with the person selling this amp, but as long as it is in good working condition (no bad caps, tranny or anything) then you are likely to be amazed by the gain you will achieve.