You definately need a phono preamp. It will not only give you more volume but will give the proper equalization to your LP's. They should sound a lot better along with having some volume.
The "Rat Shack unit will work but as already posted there are much better ones at every price from reasonable to unbelievable.
ARC SP9, HW19, RB300, Sumiko Blackbird: Front: Acoustat Spectra 22, 2 x 12" TL subs 2 bridged Crown XLS 402, 2 modified Dyna MK-III's. DBX-223XS, Behringer DSP1124P, rear: Acoustat Model 1/SPW-1, Paradigm X-30, 2 Adcom GFA-545