I honestly wouldn't waste the time or $ on stock modules. With very few exceptions, they are leagues behind the modded modules in every aspect. Well worth the extra $.
As far as recommendations:
High Gain - TONS of great options here, just depends on what flavor you prefer. I'd say consider the following:
JF Erect/Blackout
JF/Salvation/SG XTC. They're all great.
JF R'Verb
JF Venom, SLOD100, Ubersonic
Salvation Stonerverb or 50R
Salvation MarkUs (lots of love for these here)
Salvo Angel E, Mr Boga, Buddy, Mash-All, Mash-oldano, Salvado, Camerock
SG Afterlife, Criminal, or Breakneck
Ok and then there all the 5150 and Diezel mods... Just too many to list really.
Clean:
JF Vybe Deluxe (one of the most loved mods here)
JF SuperClean, TX Special, or TWox
Salvo Twinface, Baseman
SG SG/CC30
And then there are the Hiwatt mods, etc. Again, lots of choices.
Just need to pull the trigger on a couple mods, try em out. If you like, keep. If not, re-sell... That really is the beauty of the mts system.
Welcome, btw!