I don't know much about the Yukon, nor am I a man with vast knowledge of components, so I can't really help you out here, but I can offer two little bits of tangentially useful information.
1) I do have one of the Cadillac RLE 1.8's and and I love it. I tried out a few of the bigger names in the same price range at some local bike shops (e.g. Trek 1000, & Giant OCR 2 & 3), and found it to be the nicest ride of the bunch, and at 750$, it was far cheaper than the others as well. Plus some of LBSs sell the Cadillacs, so you might not have to do all the fitting and adjustments yourself.
2) Having said all of that, at 300$ you can probably find a much nicer used bike. Well, this depends on some things like where you live, and if the moons are aligned well over ebay for you (it's much harder to find a good deal there these days, I doubt I'd be able to get a bike like my Univega there for 170$ anymore)