Go vintage, do not buy a new plastic cheapo one or even an expensive plastic one!!!
My recommendations are
If looking for a machine capable of Zigzag, Singer 401A, made in 1958-1960 a little on the heavy side but has lots of built in stitches, can take the top hat cams to get a few more stitches, it's an all metal gear machine, nothing to break like on the new machines. It's a slant needle, takes common, made today bobbins and needles. an electric machine. Won't handle hours and hours of heavy duty work but will easily sew through heavy upholstery for the occasional project or the fine silk!
if you want a really good straight stitch machine, I'd go with one of the 'old black singers' if you want an all electric I'd go with a 15-91, if you want something that can be either electric, treadled or converted to handcrank, I'd go with a 66. The 66 would probably be cheaper, but it really depends on where you go looking for one. Both of these machines are low shank, taking common needles and bobbins. You can get buttonholers that work really well on them! What's even cooler about these machines is the fact that there is basically nothing on them that will break, you can easily learn to do the maintence and repairs on them yourself, which means you can save all that $ you would of spent on a tech for the newer machines on fabric!
And if you are afraid that you won't be able to make 'pretty' things w/ a straight stitch only machine, think about all the clothes that were made before the 50's, if they were home sewn on a machine then a straight stitch only machine would of been used!
All should be priced under the 150 range, with the 401 probably being the highest, then the 15-91 and last the 66.
Links to see pictures of machines I'm talking about.http://www.ismacs.net/singer/p66.htmlhttp://www.ismacs.net/singer/p1591.htmlhttp://www.ismacs.net/singer/p401.html
I really like the old machines!