2600's have the power for sure, but they don't have the low distortion and the very important signal to noise the modern Mcintosh Quad amps have. They don't have the capability of driving mis matched loads like the new amps either. Their damping factor isn't as high and if you were bi-amping with out passive crossovers like we did in big professional discos you could easily hear the difference between the direct coupled QSC amps and the 2600. It was a sad day when Mac quit making amps for commercial use, but they just priced them selves out of the market. The 2600 was my favorite Mac amp for big sound systems though we sold a bunch more 2250's and 2500's. There are four Mac amps that have a special place in my heart do to their performance and reliability at the time. MC 3500, still my favorite tube amp, The MC 2255, my favorite amp from the 80's and the little 7200 capable of oh so much more in the 70's. Lastly the 2600. You could run it all day all night for months and months in terrible atmospheric conditions and it just worked and worked. I never had one fail me driving big Cerwin Vega, double Altec and Double JBL woofers. Today I own 207's and a 206 and the 207's sound great. When I go to audition speakers I want to with 1201's or 1.2 K's. The 601's are good and the 2301 surprising with some speakers, but the 12's are my favorites today. Do they bring the same thrill as the 3500 did in the late 60's and early 70's, no way. Do any of todays amps bring me the thrill over hearing, Ray Charles, Al Hirt, Pete fountain, NeilDiamond, Peter Paul and Mary, Letterman, Sandpipers, Herb Alpert, Up with People, Christy Minstrels, etc amplified by 3 3500's live in concert with 12000 screaming fans, nope, not even close. How about my favorite disco with 18 MC 2255's and two MC 2125's, nope. And another disco with Klipsch speakers using four 2600's No Way. The amps today may all be better, but its the total experience that counts and thats why 3500's will always have that special place in my heart. Now I have had special experiences with 2300's . When the Pope came to Mexico city to dedicate the Basillica with 4 2300's pushing the indoor system and two pushing the out door system. 2300's pushing a systems for Lyndon Johnson, Hubert Humphrey, Richard Nixon, Gerald Ford and George Bush. We used 2300's it seemed for ever and though they were my favorite amps to blow diaphragms with and tear up woofers, they sounded fine. 2600's were to expensive and to heavy for portable PA work and QSC amps with their form of power Guard were my preferred choice till I retired. But they were never the Mac amps I had learned to love previously. So dream about 2600's as I do 3500's, but once you hear 1.2k's for over an hour with great speakers playing your favorite music you will know nothing else compares. Its like hearing your first Stradivarius Violin in your living room, Edwards trumpet or Trombone, Steinway or Busendorfer Piano, also, falling in love with Telefunken 250 microphones or Ampex MR-70 tape decks, there is just something special about the sound you hear from Mac 12.series amps.
If you ever get a chance hear a pair of 2600 pushing XR 290's its something special, a memory I will always have. Remember Mac speakers don't need amps with high Damping factor to control the woofers. If Mac had made a center channel to go with the 290's I would have a set. Even today. and maybe a 2600.