aluminum isn't necessarily going to bring you in lighter than steel. for example, the iro jamie roy (56cm) is only 0.1lb lighter than the mark v (56cm). and, as you know, the mark v isn't exactly the lightest frameset on the planet. the angus comes in lighter than either and is steel.

i don't know of a lot in the way of high quality frames with road geometry and track ends. street singlespeed / fixed gear frames are somewhat new to the market (well, discounting old path racers and the like. i imagine that they are going to be heavier than you'd like). i can, however, suggest that you check out the gunnar street dog. it's a pricey piece, but has a reynolds 853 main triangle with true temper ox platinum making up the rest. i don't know the weight offhand, but can be fairly confident that it comes in lighter than any of the budget offerings.

of course, if you're willing to drop ~1000 on a frameset, you might as well go custom, at which point you can get whatever you want.