The DI on my Scarlett has been actually pretty decent now that I know how to work (around it) but I also have my Line 6 Duoverb if need be but I mostly use that for bass these days.
I still want to snag simple a multi input tube pre but yeah... I'm getting the hang of things without one.
From everything I've heard though that package is quite good so if it inches me closer to realism, no matter how incrementally small, it'll still put me in a wicked position.
And I have actual properly recorded guit tracks running through a real 5150 (bed tracks for the album) so I can say even with GR5, with some twiddling, I've been able to get pretty darned close. I'm glad I started using it again. It just takes a bit of extra work to make, well... work.