I'm yet another programmer, but more on the development side than the design side. Also, i recently exited the market and am in a regular IT job, and have now become a customer.
I think the main thing you need to find is an designer/project-manager who knows a few different developers to work with. In my experience, the kind of development your're seeking will be either "cookie cutter" or "custom" (aka "bespoke"). In the former type of development, you purchase an application, and configure or extend it for your purposes. In the latter, you purchase the labor of a programmer to create your application.
Obviously, the former will be far less expensive. It could also be less successful, if you have tough competition -- because you're competing on the quality of your software. But, beware that custom code is very, very expensive. I couldn't see doing the programming for your site for less than $10,000, and the result would be less full-featured than whatever imeem has. (Of course, most of the features aren't visible to the users - the real work is in reporting and analysis.) Also, the graphics usually cost the same as the programming, if you want it to look "legit" - so, another $10,000. Just to be realistic, I might give a quote of $30,000, because you will have a lot of media, and that takes some domain knowledge, as well as additional code to handle music uploads and downloads, in bulk.
Software isn't cheap. Even if you hired foreign programmers, you'd need to have a local quasi-hacker to translate what you want into what you really need. The artist would cost the same, because it's hard to get the right "look" from someone in another country.
Now, if you just need a spartan looking site, and you find canned software that works, you can get the thing going for a lot less money.
Also, all that said, there might be something to be said for testing your idea out without software first. Do it "by hand" for some clients, first, then see if the like to pay the price you're asking. Identify the need, and fill it, and see if it's profitable. Maybe you can do it by installing PCs to play music at the stores. Then, once you know it works, take the concept online. All the money spent up-front to build your catalog, your relationships with the copyright administrators, and stores will serve as a barrier to entry for competitors. Make the site plain, and hard to access at first, so the competition can't copy you immediately.
There's a lot to be said for developing the product before the software, because changes in software cost more after the system is operational and public.
