A poor mans Rivendell is a lugged steel bike, not some brazed steel or aluminum crap, lugged steel and lugged only, otherwise you wouldn't like a Rivendell.
I think the lowest price one is indeed the Velo Orange Rando as one poster pointed out, lugged frame with lugged fork $500, not a bad deal, and the lugs look very nice too, and the fork uses the classic style flat crown with lugs. Very nice looking bike.
http://store.velo-orange.com/index.p.../rando-74.html Even comes with downtube shifter bosses in case you want to make it look vintage. Take a close up look at that frame, it really has nice looking lugs.
If you want to go vintage just hop on E-Bay and get the entire Suntour Cyclone group, these can be found pretty cheap...cheap compared to trying to get new Ultegra group, but they were the best friction shifting system in it's time besides Sprint and Superbe, and they were extremely reliable; and you can find them either nos or nib if you watch long enough. Or find the older Shimano SIS group or 600 group, these featured downtube shifting the sis had index shifting, these were very reliable.
Anyway, there's all sorts of options you can do, mine is just a couple of ideas.