Just given this a little bit more thought.
A win against Somerset guarantees qualification - and almost certainly a home QF. At a minimum, Kent, Surrey, Middlesex, Essex, Sussex and Somerset would all not be able to match a 17 point haul. That would leave Glamorgan and Gloucs.
A tie or a no-result would almost certainly secure qualification. Middlesex and Kent wouldn't be able to match a 16 point haul, whilst Surrey, Essex, and Sussex could only equal it. And that is before considering all the matches between the other eight sides - points will clearly be dropped all over the place.
A defeat would likely mean that Somerset themselves finish above us. Whilst also presenting fairly open goals for Glamorgan and Gloucs to overtake us. So it would most likely come down to whether any of Sussex, Surrey or Essex have a storming final week. But again, sides will be dropping points all over the place - so I'd still give us a solid chance of progressing with our current points tally.