Craigslist has the best deals if you can do some basic work to get it riding right. Other than that a good source is play it again sports. Very underrated in my opinion. Can get a quality used bike there. Also search for local community bike shops, many have used bikes for sale.

I loved my sirrus but get the right fit (sloping top tube needs consideration). Wheels were OK. 32mm but I had trouble with the rear (I am 245lbs and ride a bike pretty damn hard, rocking and lots of miles, etc). You will probably need a wheel upgrade to a better wheel about 1000 miles in if you are like me. This may also be the case with the others you looked at, though, just an FYI.