I likely will never buy a modern plastic machine again, after the ones here are done. I like maintaining my own machines and I can with the older Singers. Also, the metal machines just don't wear out, and there are still parts around for them.
I think looking for a gently used machine is a good idea. The new ones are way too pricey. I can afford them and I choose not to buy them anymore. My last machine, a Janome 11000 is working well and I like it. However, when it stops, no more fancy machines. A machine that costs what a good used car is worth, or a good chunk of a downpayment on a smaller home is not what I'm willing to buy.
Have fun with the search. It's always exciting. And let us know what you end up buying! I'm sure you'll love it whatever it may be.:)