The ones of the Catalyst amp series that were added in the last updates are a pretty good start IMO as they are easy to deal with.
My other two favourites are the Super Reverb and the mentioned Grammatico GSG, even if the latter is a bit tricky to dial in.
Personally, I think that some of the cabs chosen as defaults don't exactly do the amps justice too well. As an allround testing cab (I usually don't use combined amp&cab blocks but separate them) I really like the 2x12 Mandarin30 cab (default settings are fine, sometimes I switch to a 57 mic), which is working fine for both cleans and dirts.
Out of the dirt pedals, I really like the Top Secret OD (DOD 250 clone), but I typically pair it with an EQ following, as the TSOD at lower gain settings doesn't have enough output volume to boost an amp. The drive itself sits nicely between overdrive and fuzz, when you push its frontend with a Kinky Boost, it's even more fuzzy and cleans up great (in case these kinda sounds are your thing). Kinky Boost, Top Secret OD and Voltage goes like this: