I have hired developers to work on an ebay-like website for a particular industry (using LAMP, PHP) but after two attempts, I have been left with two semi-completed websites. I am now deciding between continuing work on the 2nd incarnation or starting from scratch for the 3rd time. The code is OK and mostly functional but there are so many issues it may cost less time and money just to start again.

Issues I've encountered are:
- As it's quite difficult to make a solid prototype for the site, specs change slightly as the project develops and processes become clearer.
- Development teams have proven unable to work out certain tech issues and work grinds to a halt.

I feel a lean development philosophy should have been used and also I should have built the site in smaller steps.
Having a background in programming going years back, I also feel like learning about the nuts and bolts and just doing it myself, but it would be a great undertaking (touching up on SQL, PHP, so many API's, configuring it all etc.)

At the moment I am stuck in this 'develop and throw away' cycle, any advice?

Thanks in advance,
AC