I just purchased the audioengine A2. Sounds awesome but is definitely missing on the lower frequency area. I'm planning on adding a powered sub to the combo but am not sure how that can be connected as, unlike the A5, the A2 does not have a sub-out.

My main source will be my laptop so I was thinking the connection will be line out from laptop -> subwoofer -> A2. I'm a newbie in this so I'm not sure if this will work.

I was thinking of getting the Audioengine S8 sub as it has a line in and RCA input so I can connect from laptop's 1/8 to the sub and then out from the sub to the A2. However, the S8 is pretty pricey at $399.

Also, any recommendation for a cheap, powered sub between $200-300?

Generally you would want a sub that has speaker level inputs. You put it inbetween your speaker output and your front L/R...