My friend and I have invested $40-$50 k in a website we are launching in April. We have full time jobs but put all our savings into this project. We are done with the development phase and are currently doing bug fixes and user testing.
Marketing Planning Startup Costs
Well, I think the horse is already out of the barn. The marketing plan would have come in handy before spending the $40k-$50k. But it sounds to me like you need more than a marketing plan - sounds like you need a business model. You might want to take a look at the Business Model Generation book. It will help you organize all of your strategies and perhaps come up with a better launch plan.
To answer your original question, I would not launch without a marketing plan. The reason is that you only get to launch once. This is an opportunity to build excitement and anticipation around your launch and pre-build your beta-testing list (not to mention email marketing list) before hand. Don't waste the only launch you'll ever have.
It looks like you need a plan, and marketing is just a part of it. You are planning on a bug free website. I have never seen one. The biggest potential bugs you have yet to address is marketing, and testing.
As a site for potential testers, you might be able to use mechanical Turk by Amazon. Are you testing the website or the product?
If you are too busy to do it yourself, why not outsource marketing to someone who has a proven track record?
With your guidance, a marketing specialist can help effectively sell your product for you.