I have 1 of every Lee Jackson head I could find, and I have also owned a Legacy... I still have the cab.
I have a Metaltronix, XLS50, XLA50, Ampeq VL502 and a Crate Stealth. the XLS and VL502 are really good hi-gain amps, and you can find VL501/502s on **** for around $400, which is probably about what it would cost to get your Legacy modded.
the Legacy sounds good with effects in front of it, but I dont think its really a hi-gain amp, I was never able to get a good tone out of mine... but it did look cool.
mpx