I'm going to assume that you like the vintage stuff. The Mach 2s have their fans and much of the younger generation doesn't understand that Rat Shack was a real player in the 70s and 80s. The Mach 2s can be the anchor of a serious system.

I would look on ebay for speakers and amplifiers. I would not buy cassette decks or turntables from ebay as they tend to be DOA and not well cared for. Local Craigslist is more acceptable since I can go look at the stuff first. I would only use Craigslist locally. Prices will tend to be cheaper than ebay. Audiogon.com is another site that will have lots of good used stuff. Prices will be higher, but the quality reflects it. You can pick up used cassette decks and turntables on Audiogon with more confidence.

I would get rid of the EQ. They were very popular through the 90s and still fetch high prices on Ebay, but they really are ineffective if not used right. You really need to get into 32 band digital EQs as a bare minimum, with 64 band parametric being even better, and $3000+ Wadia room correction being ideal.

Finally, I would examine vintage 70s and 80s Japanese stuff. You want the stuff actually made in Japan, not Tiawan or Malaysia. Look at Pioneer, Yamaha, Marantz, Akai, ect. You will pay real money for top vintage, i.e. $300+ for a Yamaha 2020 receiver or $1000+ for Yammie NSM 1000 monitors or $600+ for certain Akia reel to reels, but there are some real steals to be had for less money with little brother models numbers. Troll around on ebay for awhile and you'll start to see paterns developing for what is highly sought after and what is a bargain.

You've got your impulse buys out of the way to tide you over. Now its time to start looking around more seriously.