It sounds to me like you are buying ahead of your knowledge, which is an extremely financially dangerous thing to do.
That is why I'd rather buy something that is certified.. Alas, it doesn't bode well with me buying something like that on ebay..
Forget the cert. If you buy from a trusted seller, even online, they're not going to risk duping someone for one small sale (small to them, not me; I've not yet spent that much). I've kind of had it with certs. I think they're the dupes and sort of ruining the hobby. And then if you wish to sell later, sell to an educated buyer who doesn't need ngcs blessing to conduct business.
$1624 is the current melt value of the gold so $1700 is not that much of a premium. However these are pricey coins I would suggest that you wait for the right example to purchase. If you settle you might be dissapointed later when you see a nice slabbed 1927 come along for not a whole lot more.
I think I would scoop this PCGS MS62 up if I were in the market for a St. Gaudens. http://www.greatcollections.com/Coin/89384/1927-Saint-Gaudens-Double-Eagle-PCGS-MS-62-OGH If you have to have a higher grade, this one is a little bit more. http://www.greatcollections.com/Coin/92308/1927-Saint-Gaudens-Double-Eagle-PCGS-MS-65 This one is MS64 and the "buy it now" price includes Buyer's premium. It looks pretty nice. http://coins.ha.com/c/item.zx?saleNo=131305&lotNo=22410 Good luck in your search.
If you are unsure about your skills in grading, details and being genuine, then go with a certified coin. You'll be satisfied to know you bought something you'll feel good about. Or if you ever sell, you'll probably get all your money back, plus some.
I don't particularly want to cross-post, but I bought the coin, NGC MS 63 for $1950 http://www.cointalk.com/t221976/
I think you may be able to get that one coin from your local guy, just give the guy a call and tell him you're interested but the price is a bit steep for your budget, then offer him $1800. He may sell it to you or he may not but if you don't ask you'll never know. I have seen very nice double eagles in the $1800 range so you won't have a problem getting one. I know for a fact you can get one in California for $1800 but your area may not have them. I have bought at least 7 or 8 gold coins on ebay and I've never had a problem