Canada Computers have some solid prefabs that can match your needs. The people at the merivale location at least know their stuff and don't seem too pushy. Buddy got one for 3 grand last year that's a solid gaming rig. Could have saved some bucks building it himself or having me do it for him, but just wanted to get it and be done with it. I prefer to build em myself, and usually by most of the parts from there, just finished a build today. Their prices are competitive with amazon and other distributors, sometimes have great sales on top of it. I always prefer getting big parts locally incase you get a defective piece, can just drive and swap it out instead of waiting for shipping.
If u want advice, lemme know what you're looking for and DM me or something. I'm not an expert by any means, but I've been building my gaming and work rigs for the past 20 years.