Aragorn covered it well. I also agree with Mike a C&R is a great thing to have for online purchases. I actually use mine more for in person stuff at auctions but either way it's saved me a ton of time and money.

I'd be real cautious of 03s unless you know what to look for... as mentioned there are now a fair amount of reactivated drill rifles out there, and the low numbers are also unshootable for different reasons. One thing is you probably won't be an expert on the gun before you buy it, but you'll have a lot better idea once you get one in your hands, go over it, and find out about all the variants. Collector quality books are always a good investment as well for specific areas of interest - the Honeycutt and McCollum books on Arisakas come to mind.

One thing I see missing is Swissicon rifles. If you want in on one do it now. K31s are going up fast, and it seems like the last of the of the 89/11s and 1911s in distributors are gone too. Ammo is out there. They are probably some of, if not the, best shooting milsurp bolt action rifles out there. Quality is fantastic as well. Just avoid the earlier 1889 Schmidt-Rubins as I recall you can't run them with modern GP11 spec smokeless ammo. Maybe not as easy to get as 8mm or x54r new, but it's in pretty regular production from what I've seen thanks to PPU and there is a decent quantity of surplus out there right now which can't be said for 8mm or x54r.