I'm building up a TT/tri bike and I need a frame to complete the package. I'm on a budget, but would like something competitive for both disciplines.

Some ideas could include, the aluminum specialized transition, aluminum cervelo p3, an older model trek equinox (preferably the carbon version if possible), one of the older aluminum scott plasma's, or any other ideas you may have. Carbon isn't necessary, but I would like something with good aerodynamics and not crazy heavy. Looking to spend 500-700 on a frame/fork/ and possibly seatpost (if a special post is required) combo.

Thanks in advance for any thoughts you may have!