There's no reason for you to spend that kind of money. Mac uses the Svetlana KT88's, which you can get from Kevin Deal at Upscale Audio for $45 a piece, in matched quads. Actually, since the Mac has biasing on each tube, if I'm not mistaken, matching isn't even necessary, but I would still do it. Don't bother with the Sovtek KT88 - not in the same league. You could try Electro Harmonix 6550, which looks exactly like a KT88 and can be used in the amp. It would add a little more detail and treble definition, it that's what your looking for. If you want these, I have an extra set of 8 new ones.
The Tesla KT88 is another choice, although their reliability and longevity has been an issue in the past. Sources tell me they sound similar to the Svetlana, with more treble detail.
The Tesla KT88 is another choice, although their reliability and longevity has been an issue in the past. Sources tell me they sound similar to the Svetlana, with more treble detail.