Dynaco ST 70 - Best mod value?

After reading Peter Breuninger's, "The Classics," in Listener (Sept/Oct 2001), re: the Dynaco ST 70, my interest was piqued and so I therefore went out and picked myself up a nicely maintained unit. Initial impressions, haphazardly setup with some old gear hanging around in my basement...CJ pre, Tannoy Royal Blue Monitors, first generation Rotel CD player, confirm this amp as the bargain-basement audio gem perhaps of all time. At any rate, I've now got the bug to take it up a notch, choosing from among the multitude of mod option/package offerings. I am wondering whether any of you have had any experience in this regard? Among the choices I am aware of/considering are the Welborne/Alan Kimmel mod, Van Alstine, Curcio, Triode Electronics. I welcome your comments/advice.