The GSP 1101 was (and is, somehow) very good for the price. I still keep it though the Kemper has made me forget about the good old bloke.
Had a 2101 back in the '90s. CJ.
It had some killer "shred" sounds. Didn't even audition the cleans, which is hilarious 'cause I can't shred.
IIRC, it used a 12AX7 tube in conjunction with "modelling" to achieve its tonez. Superb unit overall 'though; I miss its "coolness". The FX were excellent, as one might expect from Digitech.