As long as you are not reflexively jumping at a bargain, i.e., it is a model you want apart from the cheap price, you should go for the deal. Something like a preamp should last a lifetime and will not be significantly degraded in performance--it will be like new. This not like a CD player or a phono cartridge which will wear out and have a limited useful life (in which case you are buying the remaining life of the item without knowing how much use was made of it).
