IMO, you'll have a hard time getting a decent amount of money from that stuff...I mean...I bought my entire Pentium 3 retro PC, with matching mouse and keyboard, for $13 CAD, from a PC recycler / refurbishing center. The P4 is maybe worth $5...the board, maybe $20-25, the GPU, maybe $10-$15. You might be able to get more if you put them on Ebay and aren't in a rush to sell...or they could never sell. Honestly, it's almost hard to give away hardware of that age, as it's not really "retro" to most people, but not new enough to make a modern PC...and super common.