the only ones that might fit your bill are funds that are already in that space... so yes, partnering might be the way to exploit your edge... i know some investment banks will let you co-lo next to their infra at NY4, NJ2, etc... but you cant be a two legged individual... i dont know what you are doing now, but if I was you I would focus first on reducing my latency to current prime..
I want the most optimal path for tick -> process tick -> spit order out, one exchange at a time. Some exchanges are less important than others and some latency is OK on some paths, but every colocated system needs visibility for the rest of the market -- even if the view of the rest of the market has some high levels of latency. So for example, say I wanted to be a fast gun at BATS -- I'd want a very fast setup to take a tick from BATS, spit an order back to BATS (or cancel) -- but, that box at BATS can take a "slow" feed from other exchanges and have a consolidated feed input from other until I'm able to plug in something better. (So I'd be fine with microsecond latency on one exchange, but outrageous multi-millisecond latencies seeing other exchanges.) My current prop firm gave me a good fee structure and good connectivity. What they didn't give me was good technology. Their order placement server is several milliseconds away from the most optimal quote servers (closest to exchange.) I've tried to get them to make some structural changes, but they have other technical problems they're trying to address that don't align with my interests. So I have two choices: Find new edges that don't need speed and work around my prop firm, or, alternatively, look for ways to leverage my firm's existing clearing/exchange relationships, but somehow piece-meal the technology into place to get speed -- so I can improve my current edge.
Some hosted, broker-neutral options here: http://www.rtsgroup.net/trading/rtd-tango and http://www.ezxinc.com/asp.html http://www.ezxinc.com/ezoms.html I'm not on either right now so working from memory here but I believe both were in the TT / bloomie price range. RTS if I recall would have had more access than I was comfortable with, the second company EZX was good peeps who knew their shit and were super willing to help. Told me they could walk me right through the FIX cert process for multiple brokers, I had to go a slightly diff direction for unrelated reason but they would still be on my short list.