- Style it up a bit using twitter bootstrap. The main button looks awkward.
- Found a small company (UG) with 500EUR capital to hold rights on the site if you want to further professionalize this project.
- Add caching for search queries (it took ~ 10sec to calculate 800€ and 100€ which might be some of the most requested price points)
- Add large buttons at the top which show the most sensible price points
- As the others have said, this is easily expandible to other european countries. Add a French / Italian / Swedish version.
- Add some social stuff so people can comment etc
- Take some inspiration from PC parts picker
If you want to talk feel free to shoot me an email.