your putting on just coilover springs right now right?
if so, you won't need a spring compressor again, you'll only need it to remove the STOCK springs. b/c coilover springs don't compress.
there's 2 different kinds of spring compressors also, the one I used costed $50.00 to buy. You should just rent it, since you'll probably NEVER need it again, EXCEPT to install coilovers on another car maybe.