If you've got 7K worth of mods on your ride, throw it up for sale on a site like this one for a little over book value...which is probably nowhere near what a dealer would give you. In fact, they're going to offer a decent chunk less than book value.
Selling it here you might find someone that will see some "value" in buying your ride "as is" a little over book value as they will appreciate (and understand) the modifications that you've put into it. If you go the Autotrader, Carfax or Craigslist route, you're opening it up to the general population...the majority of which DGAF that it has a bigger turbo or upgraded intake/intercooler or whatever...
This is assuming you don't want to spend the time and effort in parting it out because without a doubt, that's the way to go that will net you the biggest return. What I said above is probably the next best approach.