Reply to Pioneer CDJ-350

So i havent been dj'ing for too long....but i am fully obsessed. Its bad to say the least....

I have a VCI-100 Arcade with the NI audio 2 and I love it. I would like to add some CDJ's to the setup. I would love to find some CDJ-900's but i dont want to dive into something so expensive without even knowing if i will like them. I found some CDJ-350's for $250/each lightly used....Would love to hear some thoughts on both the gear and the price.

Also, im assuming that will mean i need at least a 2 channel mixer? Correct me if im wrong (which is very likely because I am very new to all this) but i cant use my vci-100 as the mixer for the cdj's right? With the assumption that i cant use the vci-100 as the mixer, i found a DJM-600 for like $500 used. Im going to try and buy it for like $300-$350 max. Thoughts on the pricing?? Is this mixer outdated?

Again, i apologize if some questions are stupid but im not trying to just throw away money without knowing what i am getting myself into. Any and all help is much appreciated. Thanks.