I'm totally biased so take this with a grain of salt... Kush Audio Electra EQ. It just gets me from point A to Point B effortlessly without mucking with the character of my source sound. No matter how you turn the knobs it just won't get harsh or grainy. There is some serious capability to sculpt the low end between the proportional-Q low mid band, fixed low shelf, and variable high pass filter. And it's a killer affordable price.
I also really like my True Systems PT2-500 preamps. I know transformerless clean preamps aren't high fashion, but this thing has a detented pot with great feel, a meter, HPF, and a DI input with thru jack that I recently discovered is capable of capturing some of the BEST bass tones I've ever recorded. I had been dismissing/overlooking that DI for years. Never touched it. The one day a couple months ago decided to plug into it. It was MASSIVE! I was really impressed.
I think the Lindell modules are a great buy. I have the compressor which is very useable on many sources. The blend knob, sidechain HPF and meter are nice touches. Overall build quality exceeded my expectations for something that affordable. I've also heard the Pultec style EQ at a friend's studio. Again, more sound than you are paying for.
I would say all the CAPI stuff...especially the VP28. Love the Missing Links (VC528)...Avedis is really nice. The Heritage 1073 was great. I loved the Anamod 660...I have a soft spot for the Helios stuff...but I do think there are options with "better" headroom and general use. I was also impressed with the Neve 1073LB.
In addition to the CAPI stuff, I'd say you should grab your choice of flavor of API EQ... they're such a standard and are so useful, I think they sort of define "must have" in 500 series. There's an abundance of great 500 series products out there now, but I think API EQs will always be valuable tools.