"...an easy $300 or so less, and the same for a Garand..." Nope. $445 and up for an M1 rifle. $479 and up for a carbine.
Shevrock. Jump the hoops, shoot the matches even if you don't have to (it's great fun and you'll meet some great people who will usually let you shoot their rifle. Plus there are quite often loaner rifles at the matches) and buy from the CMP. You know what you'll get(a pretty stock doesn't mean the rifle is any good.) and the CMP isn't happy until you are. Have any issues and they'll fix it with a phone call.
Go here too. Good bunch.
http://www.odcmp.org/new_forum/
Here's a list of what gets done to a CMP M1 Rifle before it's put up for sale.
http://www.odcmp.com/Services/Rifles/inspect.htm
They sell Greek milsurp ammo too. Carefully loaded handloads it ain't though.
"...that hold their power against the test of time..." As in value? Nearly every milsurp rifle. They're an investment you can play with. The thing with milsurps, in general, is that none of 'em are being made anymore and the condition of most available examples is going down(That usually doesn't apply to CMP stuff too much though. You get a safe serviceable rifle.) and the prices are skyrocketing. My M1 rifle cost me $175Cdn, 30 years ago. I've seen junkers at gun shows, up here, for $775. The guy did carry it back and forth a lot though.
Go buy a copy of Hatcher's Notebook and Hatcher's Book of the Garand. Your local gun shop or Amazon. About $30 or so each. The Notebook is required reading for anybody who shoots. The Book of the Garand has a history of the rifle and a trouble shooting chapter.
Plus there are free, downloadable, TM and FM manuals, in .pdf format, available here. Note the need for the provided UN & PW.
http://www.biggerhammer.net/manuals/
"...haven't found many m1903's around..." They have issues according to the S/N. Hatcher's Notebook will tell you all about it. Mind you, it's a 100 year old milsurp rifle. Lots of 'em have been sporterized(bubba'd) or destroyed in one way or another.