I think you hit the nail on the head with your thoughts about a Kickstarter. I am much more likely to pony up more money if it is "guarantied" to keep the project going. Kickstarter also has the potential to put it out in front of a larger audience. It also gives you a place to lay out your case for the site and explain the costs.
I really hope you will consider doing this and then those of us who have been using the site and the app can be out promoting the Kickstarter to others. It is possible that we really can raise the kind of support needed to keep things going. It might take a few months and the site may have to go offline for a bit if the money does not come in quickly. As much of a bummer as that would be it would give all of the current users a kick in the ass to help get more supporters.
Would it be possible to keep a version of the site online with a place to download popular tracks, but without the track creation function? It could act as a placeholder and be another venue to promote the Kickstarter.
Have you considered reaching out to vendors as part of a Kickstarter? Kickstarters usually have a tiered set of rewards for supporters and one of the higher ones could be geared toward commercial support. Perhaps a $1000 contribution gets you an ad for a fixed amount of time and discount on future ads to reward the support of the Kickstarter.
Yes I said ad. I think the reality is that you are going to need to seek some kind of continuing revenue if the site is to keep going after the update. Ads could form the base of that with voluntary user support shoring that up.
Please let those of us who have been benefitting from the site do our part by giving us a chance to evangelize/fundraise for you with a Kickstarter. You have done all the heavy lifting so far and now the users of this "free" site need to step up.
And if you have to throw in the towel for personal and financial reasons do not see it as a failure, just as an inspiration of what is possible to serve the riding community.
Los Alamos, NM
"You have never really lived until you have done something for someone who can never repay you."