Somebody mentioned a Singer 99, and I love mine, but I certainly wouldn't call it lightweight. That thing is like a boat anchor!!
A couple of places to check out that nobody seems to have mentioned. Overstock.com has some great deals on machines; I bought an embroidery machine and a serger from them. Get on their e-mail list because they send frequent discounts that can generally be used on anything. Another source you might check is wawak.com. They also frequently discount machines.
And just because I feel compelled to mention this every time the subject comes up... this was verified by someone on this very board who called directly to a manufacturer. The idea that machines made for big-box stores or for home shopping networks are made differently is a MYTH. Thus, a Brother is a Brother.... a Singer is a Singer... and so forth. They're all made in the same factories. You may find slightly different models of machines in different places, but it would be cost-prohibitive for manufacturers to set up different factories, one with cheaper materials. So if anybody tells you that (including a dealer) it's bunk.