Hi FloppyPoppy,
I'm currently re-working the way we allocate VRAM for screen-sized textures so that we can re-use memory more easily, because these textures are one of the major contributors to VRAM usage, especially when running in higher resolutions. So you can hopefully expect some savings here on the next release.
After we've allocated the required VRAM for the base engine we then give much of the remainder to the texture streaming system, because the more textures we can keep in memory then the less likely you are to need to stream a lot of textures off-disk quickly which can introduce cause visual popping and increased disk IO.
If you've seen blurry textures then this is almost certainly a bug in the code that determines which resolution texture to stream and not a problem with the amount of VRAM you have, therefore I wouldn't recommend more VRAM in an attempt solve this issue.
For now our optimizations are primarily for more 'typical' resolutions, but further down the line we do plan optimizations that are specifically tailored towards multi-monitor / 4k, and at this point we'll have a better idea of our ideal VRAM requirements for a silky smooth experience on such setups.