I originally wanted to keep it around $1300-1500 per person so it was affordable for guests, and was looking in Punta Cana but I ended up at Dreams La Romana because I had heard great things about it, and most of the resorts that had the quality we were looking for were more than our initial budget. In the end we couldn't get anything over a 4 star for that price and since it was my wedding, I didn't want a run down place - so it was Dreams Punta Cana or La Romana - just chose La Romana because it was a quieter area, more relaxing beach time and less partying time which is more like our personalities.
I emailed a bunch of different travel sites - selloffvacations, escapes.ca, etc all have actual travel agents that you can email inquiries to and they will give you suggestions - I worked with Wendy at escapes.ca and she was very helpful and honest about her suggestions (and even gave me a few of the "these are supposedly 4.5-5 star resorts but I wouldn't send you there if you begged me" type of suggestions as well.
In the end, you will probably drive yourself crazy trying to pick a resort because there are just SO many, and so many of them will be awesome! I would suggest being a little flexible on budget per person as sometimes the difference between $1300 per person and $1450 per person will make a HUGE difference in quality of the resort but probably not make or break a decision for a guest to attend (if they are already spending that amount of money, the extra $150 is probably not a deal breaker for most)