I have a few of these, not least because I actually read all of Homestuck out loud to my sister a few years ago (she is disabled and cannot read complex sentences). It becomes a lot easier to nail how you think a character should sound when you're trying to voice them yourself.

Karkat: Richard Horvitz. Obviously this is a popular one he has in common with Caliborn, but it WORKS, dammit! My one stipulation is that I actually don't want him screaming all the time like in Zim, I'd much prefer a more ornery take on Raz from Psychonauts. Calm, but nonetheless filled with distain.

Jack: Steve Blum! Yeah, I guess I'm on kind of a Psychonauts kick, but what do you want, he's good at voicing deadly men in suits.

Droog: Tom Kenny. That might sound confusing, but I actually really like him when he's doing lower-key stoic or intimidating roles. He's really a man you can throw at almost any production and get a great performance.

Eridan: Trey Parker doing Jimmy on South Park, without the stammering. The "wwavvy accent" is really hard to interpret as an actual voice, and I think turning it into kind of a young Elmer Fudd voice is the right call. I wish I had a better example of this than fucking South Park, but that's what I got.

Cronus: Ben Schwartz, in his usual "piece of shit guy on a sitcom" shtick.

Doc Scratch: Keith David, specifically the kind of performance he does as Flame King on Adventure Time. Comedy with some menace behind it. I know a lot of fans imagine Scratch as having a higher, more condescending tone, but I think about stuff like the "lies of omission" speech and the little growl Keith would put on "No one can have all the facts. Only I can." and get chills.

Caliborn: Not Richard Horvitz, but Justin Roiland! Or, well, it used to be him, before we all learned he was kind of a shithead. I'm on as much of an Adventure Time kick as Psychonauts, but I always felt that Lemongrab's stilted "having to consider each word that comes out of my mouth for a second before I say it" performance fit well for Caliborn, who obviously isn't all there.

Jade: Lauren Tom. Between Amy on Futurama and Connie on King of the Hill, I think you can imagine how her voice and that dialogue goes together.

GAMZEE AND KURLOZ: Obviously, in the TV adaptation, you would simply get Violent J and Shaggy 2 Dope to voice these two. I don't even really know what they sound like. You just, you gotta do it. It's right there.

Dave: Uh...me, doing a shitty Critikal impression, I guess? I don't even watch critikal that often. But I feel like my mediocre version of his voice really nailed Dave better than any other character I voiced during that readthrough. You need an affect of a dude trying to sound cool but coming off a little bit dorky.

I'm pretty sure I had more, but I can't remember them all right now, and I'm not gonna just make up new ones to fill out a post.