Cinder blocks make fairly decent speaker stands. I frequently recommend them to "newbies" who usually sit "bookshelf" speakers on the floor (not good). The usual thing is to upgrade the weakest link. Have you considered a new stylus for your current cartridge or a better cartridge? Nice IC's and speaker cables are an upgrade that cost wise ranges from reasonable to "Are you kidding me?". At your present level BlueJeans (nice reasonably priced cables) cable will probably suffice.

You don't mention any kind of digital playback capability. Are you bypassing CD's? If you're using a DVD player or budget CD player for CD playback an external DAC is the best bang for the buck upgrade. Grant Fidelity and Emotive sell nice DAC's that are reasonably priced. The Grant Fidelity has a switchable tube buffer and the Emotiva is some seriously nice looking eye candy. In any case, replace/upgrade what you think is the weakest or least satisfying thing.

This hobby is all very personal and very subjective. Please your own ears and you won't go wrong.