As a fellow noob to this forum, I have found that it's really easy to get the answers that you need just by looking through the past threads and searching with relevant terms. Good luck.
gofar99 Messages: 1939 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
Hi, I would start with a google search. Subs are often on sale from main stream companies. Places such as Parts Express, MCM and Audio Advisor are frequently selling some off. I even got a pair of Martin Logan 300s for $99 each with free shipping that way. If you find something and don't know how good the seller is or the product is just post the question.
If you've just bought Focal Aria 905's I can see why you don't have a large budget, but they are very good speakers! Without knowing how you're going to mount them, or whether you are after music and hifi or home cinema use it's hard to recommend a good subwoofer. Could you give use more details?