I agree with you, the Krell and ML may be the best of your 5 choices. However, at their age, and as hot as they run, they will probably need their caps changed soon, if they haven't had this done recently. So I would look for ones that have recent (within the last 5 years) service with caps already changed. Otherwise you may as well contact Krell/ML now and find out what it will cost to replace caps, then figure that into your budget.
Cheers,
John
Cheers,
John