Kt88 or 6550 tube for McIntosh MC275

Hi,  

I have a MC275 comes with original McIntosh KT88 tubes.  I am wondering if it is worthwhile to try other and what to try.  First question is, do I need a match quad?  Or I can get away with two matches pairs?  If I need matched quad, then it seems my only option is to get new production tubes as the NOS matched quads are very expensive.

For new production, I did some research.  It seems people prefer KT88 over 6550.  And the two brands for recommended are SED and Genalex Gold Lion reissue.  Are they better than the stock McIntosh tube?  Or should I save money and upgrade my other component such as my DAC or adding a preamp first?

thanks.