I know this is an odd question, but... how do you define "amazing"? (Or to put it another way, how much do you know about the original Apple I/other similar systems of its era? If you think it's going to be "amazing" because it's somehow a precursor to the Macintosh, or even the Apple II, you'll probably be somewhat disappointed. The Apple I was essentially a dime-a-dozen minimalistic 6502-based computer like a KIM-1 combined on the same board with a video system mostly derived from Don Lancaster's TV Typewriter Cookbook. Probably the one most innovative thing about it was one of the earliest hobbyist machines that used DRAM instead of SRAM for main memory; DRAM appeared at about the same time as affordable microprocessors but its timing requirements made it tricky to incorporate into designs like the Altair.) Unless you want to play with 6502 machine language you're probably not going to be that impressed with it.
Anyway. If you're serious about wanting one of these ask about it on Applefritter. The guy who makes the "best" Apple I kits hangs out there, and I believe he's had a few choice things to say about the outfit that makes the board featured in these eBay auctions you're looking at. In any case, realistically it'll probably cost you at least $500 or so to buy all the parts to stuff it. (An outfit called Unicorn Electronics will sell you a complete set of parts minus the board and ROMs for $666.66.) Expect to pay more if you want the date codes on everything to be 100% authentic. Some of the parts on an Apple I, particularly the shift register ICs used for the video memory, simply haven't been manufactured for quite a long time.