I see no reason under RAW why you would restrict attacking with two hands or with power attack, or with any other special ability usable on a normal melee attack.
That being said, a scuplted whirling blade, wraithstriked, power attack for full, with a spell storing greatsword holding a 12th level vampiric touch and a channelled lightning bolt from the spellsword ability makes for a very bad day. Of course, the channelled spell will discharge into the first target hit, but it still makes a bad day.
In case your wondering...one of my players did this on a regular basis. It was part of the abuse of wraithstrike that has caused my great wand of nerf to descend.