you can find some amazing D300 offers,trust me. & you can get it cheaper than a new K7. & adaptors are just as good for all brands,since they are not really complex mechanisms.
Yes, Pentax isn't "the same as" the more heavily advertised and popular brands - but sometimes, one's journey can be more interesting and educational - if taken by the road less travelled...
there are a lot of reasons technical & quality wise why Canon & Nikon are "better" for the general market,photographers & amateurs alike. this is not about being popular. And about the stabilisation advantage you were talking about,care to make some direct comparissons with Nikon lenses,price-wise? (without including Sigma lenses)
,I'm not hating Pentax for their lack of development strategies & marketing,I just like to advice people for the best quality/price options.