hi connemmara, my advice would be to for "antique" (second hand!) because you get more diamond for your money. If you find a ring you like, you can always get the shank changed to whatever gold you want very cheaply. I did this with my engagement ring, which was much cheaper as an antique than an equivalent ring in jewellery shops, and got the shank changed to white gold because i prefer that. I also like to think that tghe person who wore it before me had a long and happy marriage (although what it was doing in a shop if that is the case is beyond me:))
I got mine form an antique shop in oxford, although i have in mind you are perhaps not in england?