Hummm ... most folks comment that a Vet 30 helps tame the "harshness" or "shrillness" on a DSL40 1x12 combo. Sounds like it may have taken it TOO far for your tastes.
Personally, when I think great Marshall tone, I think 1960's Greenback ... nice & full, but also with a lot of throaty, urgent lower midrange ... and that's what the INVADER is all about ... a single 12 that can handle up to 50-watts and still deliver the GB sound! Soooo ... go for an Invader.