In the Thief forums there was a discussion (somewhere) that using a 23% haste setup that adds more STR, Att, DA/TA, actually beats any other setup that caps haste (this was before Neo Nyzul, mind).

That setup was:

Empy+2 head, body, hands, legs and relic +2 feet, used with Twilight belt.

I assume that now, Phos +1 belt would beat Twilight, though you'd lose 2% DA for 1% haste.