Thanks Tom, this is exactly the info I needed. I will go the extra router route. I don't see any benefit in using a specific access point. As said, this means I'll also have a backup router in the house should one of the two fail. And BTW, your home setup us remarkably similar to mine.

It will probably not be cheaper though, since I've had my eye on a new Draytek router which costs 160 euro. But those Drayteks are the creme-de-la-creme for home use. Incredibly configurable. Not for the faint of heart really, but I've used them in the past and was always very impressed with their performance. (use the "Live web demo" link on that page I've linked to to browse the router menus)

So I'll most likely use this Draytek router as my new main router, and my current D-link DIR-655 and an access point. Also, the Draytek router does not support 5 Ghz, so I need not worry about that either. Problem solved.

Thanks again for the info!