I sounds like a vibration as opposed to a mechanical noise. It's probably worth getting it checked out but doesn't sound like anything to worry about too much.
In my experience when an economy starts to recover and demand increases, prices for desirable used vehicles will also start to rise. I'm not suggesting that they will go back to what they were, but they will increase to some extent.
I used this for my race car trailer but no longer need it now since selling up. It's a very strong and high viz piece of kit that cost me over £100. Looking in the region of £60 for it. I don't really want to post it as it weighs a ton so prefer collect. See link below for details:
http://www.purpleline.co.uk/Fullstop/nemesis/Main.html