Ill make an attempt to try to fill your demands [img]smile.gif[/img]
If its challenge your looking for(you gave that sort of a hint with Ascension), I would suggest the Tactics mod(my personal favorite). It has some INSANELY difficult add-ons(such as Improved Ilyich), and some to add a bit of a spice to the old and boring encounters, and to remove the possibility of the old cheese tactics. This is made by Weimer and Co., and can be found
here. From that very place can also be downloaded the Items Upgrade mod(some overpowered items here), Ease-of-Use mod(again, some overpowering concepts) and the NPC Solaufein mod(yup, the drow), whom is romancable by both sexes, i believe. He is a Fighter/Mage, by the by. These are all relatively bug-free mods(the multiple strongholds and any race romancing thingies in the EoU mod may have some bugs, so dont install those if you hate bugs).
Then at
www.forgottenwars.net you can find some of the best NPC mods out there, and some to en-change the old ones. the Flirt pack is to add a possibility for YOU(well, the PC, actually) to initiate a limited conversation, from where you can flirt with the romancable characters. Then theres the completely new, and indeed, excellent Kelsey mod. Kelsey is a romancable male Sorcerer for the female characters, and has been praised to the heavens by nearly all whom have played him. I liked him too, and hes not even overpowered(stat wise, atleast

)! Then theres the banter-pack, i havent tested it yet, so cant say much about it. Considering that its FW made, i should think its a quality mod...The oversight mod is also to add a challenge to ToB, though if im not mistaken, it makes Sendai the nearest thing to Impossible(i heard your woes, Xen [img]smile.gif[/img] ).
Now thats about all the really good mods i can think off the top of my head,(the darkest day might be good, but i hear its INCREDIBLY buggy, so i think you should stay FAR away from it) and they are all Weidu made, making them completely compatible with each other.
Just thought of this one, the Baldurs Gate Trilogy is very good. It allows you to play BG1 with the BG2 engine. This means that the utterly slow movement of the characters is gone, you can play the BG2 classes AND the XP cap is lifted. It also includes Ascension. It does, however, have a few bugs, even one near-gamebreaking bug in ToB(has something to do with Sendai). All the bugs have a work-around though, i hear. Then theres the fun Imoen Romance(both sexes), though its kind of hard to get to work the way you want it(Imoen is sensitive). It can, among numerous other mods, be found
here.
Hope these satisfy your demanding taste