I would check resonant frequency of the arm. A high resonant frequency would make the highs less open & muddy the bass. One other note, is that the Subwoofer can affect the isolation of the turntable and then create resonances that would again muddy the bass and reduce the extension & clarity of the highs. When you integrate full range bass into any system, you now test the limits of all your equipment. This is where it really gets challenging and can be expensive.
On a note re: VTF & VTA. As I change VTA I do always recheck VTF (depending on the arm) and then reset the VTF to the previous setting to make sure I am listening the effects of the VTA change and not the interelated VTF change. I hope this is clear. All the best. I wasn't a fan of the XV-1s but it did have good bass and sweet highs.
On a note re: VTF & VTA. As I change VTA I do always recheck VTF (depending on the arm) and then reset the VTF to the previous setting to make sure I am listening the effects of the VTA change and not the interelated VTF change. I hope this is clear. All the best. I wasn't a fan of the XV-1s but it did have good bass and sweet highs.