If you really are interested in only straight and plain zig-zag, my Singer dealer recommended the Singer 20U for a reliable straight-zigzag stitch model. It's considered an industrial model, comes with a table, and an 8" harp for under $1000.00. There is a model with a 12" harp but I couldn't find any information on it.
Here's a description -- it can be found cheaper than this.
http://www.sewingmachinesplus.com/singer-20u109.php