If the ss of Subtlety is the same in 3.5 then I HIGHLY recommend it. Remember that the +4 to hit and damage stacks with the enhancement bonus, and if someone GMW's that sword then you could get as high as +9 to hit and damage. I would also recomend that you add an energy effect to the offhand sword. +2 Shock is better than straight +3. If you're not sneak attacking, then you can use this sword for your mainhand to increase your damage output.
Stick with Imp TWF. In a group combat you'll like the extra attack. If you can afford TW Defence then that sounds pretty nice. Also, if you're using FR Stuff then the Guild Thief is a good PrC. Sneak, Leadership bonuses and bonus feats are all good.
Dual Strike is not a strong feat. Will someone else in the group have it as well? Remember that you need to flank with someone who has the feat for that +4 to hit.
For a wand, try Imp invis if you can afford it. +2 to hit, sneak and 50% miss chance is invaluable. Alternatively you could look at a Ring of Blinking. 20% miss chance, but for those times when you need to stay in melee against a tank it will save your life.