XV Level 2 suspension may be a better front suspension than the Magnumforce. XV spent ridiculous amount of money engineering and testing their system. They offer some robust systems. A number of their hard parts are based off C4 vette components, so they are durable with a large selection of aftermarket support parts and numerous components in their system are more modular so they can be easily upgraded. Magnumforce has done a good amount of design work, but I've never seen much horsepower behind the why and wherefore of what they've built. Either one is going to cost you north of $6k fully outfitted.

Roadster shop seems to make good stuff. No experience with them. Certainly an IRS is a great rear end. If you are fabbing a lot of parts, then you may as well go for it. However, in a road race environment, 3 links or torque arms tend to work better than 4 links. While marginally less adjustable, they also have less potential for bind and greater articulation

IMO, best bang for the buck isn't found in any of these. Many of the fastest autocrossing mopars are actually running stock based set ups with some key component changes. Hotchkis and Firm Feel have done a lot of leg work and research into creating these system that take the already quite capable stock system to the next level or three. They also are budget friendly and an entire Hotchkis system will cost less than just one end of any of the above systems. But it all depends on what you want it to do and how you want it to do it and what rules are going to do to you with these mods. Many autocross classes are rules limited. Truly unlimited classes are running systems costing twice as much as anything mentioned here so far.