Recently modified my system. Was running 4 BOSE 501 series II's (from 1973, back when BOSE stuff was decent) and a pair of Bang & Olufsen Pentas (1988). Used a Yamaha control amp for the self powered Pentas. Had a Sansui 7000 4-channel receiver (circa 1977) for the 4 BOSE's. Ran the Pentas for front channel L/R, had 2 Bose's for front L/R, but placed them on the sides. Had 2 BOSE's for back surround L/R. The sound was impressively good, but the 1970's sound around technology is nothing like today's stuff.

Went out and bought an AR HC6 home theater speaker system (4 sats, center, and powered sub $329)) and a Yamaha rxv 2500 a/v receiver ($750). After lengthly experimentation, I ended up with:
Penta's for front L/R, running of their own amps, with volume control by the Yamaha.
2 BOSE's as front L/R placed outside and slighty behind the Penta's. Had to put 4 ohm resistors in line since the BOSE's are 4 ohm. Feared the worst, but didn't notice any audible sound deterioration.
the AR sats as side surround and rear surrounds, plus the center and subwoofer.

Basically it's a 7.1 sound system using 9 amps/ 9 speakers/ and a powered sub.

End Result: No comparison for movies/video with the old setup. Very impressive improvement.

For music I don't think I lost anything in the transition. I thought the Yamaha 2500 was quite flexible in allowing me to blend 4 large front speakers with 5 cube speakers. Still a big mishmash, but what the heck.