Here are two more options:
1. J & J Ceramic - One-piece aluminum barrel. This is a barrel I play with. It's very accurate with RPS paint and lightweight. Problem is that it comes in limited colors.
2. Custom Products CP - One-piece aluminum barrel. This is the barrel I would recommend starting out with. They come in a variety of colors, lengths, and bores. Start out with a .689 bore, which will fit your average paint on your average day. When you get more cash, you can buy the same barrel in smaller and bigger bores to better match different paints.
You can shop for either of these barrels on ebay, and pick up a brand new one for $35 to $40.