Hi Heather,
Deciding the platen size and budget is probably two of the toughest things to begin with. From there, it's just shopping.
Do you want new or used is another question.
If you want new, I would suggest you check out the Preferred Vendors list on the left of the forum. The reason is, some of them offer discounts exclusively to forum members. You'll find codes in that section. The vendors with a little yellow star offer a discount.
Go to their sites, read about what presses they carry. There is a wide variety between all of the vendors. I believe you can find just about every make and model there. Once you compare the 16x20's, the bells and whistles you can add, the perks/discounts/shipping info, you'll be able to narrow down your choice of heat press and supplier alot easier I think.
Sunie also has a good rep with alot of members on the forum. I know there is this thread:
Sunie / Seiki / Transpro Press Owners: Are you happy with your press, would you buy it again? Yes or No. Thx =)
Which is on the 15x15, but the reason I mention it is because I believe Sunie has a 16x20, and the above thread can give you some feedback on that mfg. If Sunie has the 16x20, I'd compare it in the mix of presses you will be comparing.
A press is a press is a press. As long as you buy a press with a good reputation (a good warranty helps
), then you just really need to choose those options and supplier.
If you are looking for used, I would suggest you look in the TSF classifieds, Craiglist, ebay (for brand name or the sunie press I mentioned), your local print shops that may have unused equipment they will sell, or someone closing up shop. You'll have to do the dreaded "evaluation" if you look for used, but plenty of folks go this route and get a great deal.
I hope some of this information helps you out. Choosing a press can be daunting, as well as so exciting. I was totally excited when my press showed up. Funny, isn't it? And I still love my press.
Cheapish but Good Quality Heat Press? 
