The R32 is very tail happy for an AWD car while the R33 feels very heavy in comparison, although nowhere near as bad as the W12
Both really need 350-400+hp to feel quick which is usually referred to as Stage 1 which is exhaust, air filter and 1bar boost and maybe some mapping and then they start to feel a little bit epic
Parts are now being an issue, mainly for the body rather than the engine as both cars are around 20-25 years old. I'd consider using Rod Bell as a garage if you're in the top 2/3 of the UK or AbbeyMS or RK Tuning in the south.
I imported my R34 through Miguel @ Newera Imports and the quality of their work is phenomenal, they only import highly looked after cars, although their prices reflect that (£15K+ for a R32!). Just be aware that age is starting to catch up with these quickly, so be careful because they're now at an age where they can't be replaced.