most mak's are a sealed tube & hence the mirror can remain in very good condition for a long time, a well kept celestron orange tube from the 70's can be still good today (unlike newts which are open to the air)
the thing the old mak's lack are th newer coatings on the corrector glass on the front -how much diff it makes is up to the observer.
To check prices goto the classifieds section of
http://www.astromart.com
click search in the left hand column & type in quantum 8 or 6 -- keep in mind the quantum ota's go for lower than the equiv questar model (no mount)-so if you cant find any 8 sales check the questar 7 prices & work your way from there