Upgrades/Mods for a Dyna ST-70 Series II tube amp

I just purchased an early 90's Dynaco/Panor Stereo 70 Series II tube amp in perfect working condition. I am very glad using it in my biamp system as mids/highs amp (the lows are powered by a solid state ADCOM amp). However, I am considering upgrading/modifying the Mk II Dyna and was wondering if anyone had any experience with this remake of the classic ST-70: any Web sites with interesting info? Please advise.