I use a Dip Classic between my Pioneer DVD player and Monarchy Dac, and it makes quite a difference to my ears - smooths out the top end and improves detail.  I think it depends on how sensitive the dac is to jitter in the first place.  £150 does seem steep though.  It might be worth looking across the Atlantic - they're more common there, you'll get one cheaper, and they work fine with a relatively cheap mains transformer.

Gordon