A general note: I would play through SoA at least once unmodded before you add in any MODs, even just NPCs. I haven't loaded any of the scenario or TC mods, so I can't comment on them
Tactics mod, especially with spell-50. This adds NO new majour encounters, but boy-oh-boy does it make a lot of the existing fights more interesting. It is in no sense balanced, as it increases the difficulty by a fair bit, but it is loads of fun. Item upgrades mixes well with this.
The Solaufein NPC mod is also very good, IMAO, as it adds some very nice NPC-specific fights, especially Ritual and Eclipse. Solaufein is a
bit cheesy, but very well written and much less cheesy than, say, Valen.
Both are available from
Weimer's wonderful wierd world of wacky MODs
Tashia and Kelsey are also good mod NPCs, but Tashia has less specific content. Kelsey has mucho soundests and banter, but is not a good choice for the munchkin player. Both are nice sorceror NPCs.