Ok -

- Decent shock forks are expensive and may throw off your bikes geometry; the sort of forks likely on a hybrid will repeat your experience with the seat

- Fatter tyres can eat shock, but your fork and chainstays will limit the width you can fit

- Tyres will eat relatively small shocks like the ones you are talking about better than even good forks - because tyres flex faster

- Fatter tyres don't have to be slower; you just need to pay for premium low-hysteresis rubber - go eg to Schwalbe's site and look at the speed ratings for tyres there

Your best bet is probably an all rigid mountain bike with fast geometry and fast +1.5 slicks. A cheap solution is to pick up a classic 90s race grade bike off ebay - I got a race grade Zaskar frame with ok components attached for about $300 last week in the UK; very tough, fast, agile, even lightweight. If a 1.5 slick wasn't enough suspension you could fit Big Apple balloon tyres - google for reviews, they're actually pretty fast and the shock absorb is just immense.

You could also try a better suspension seatpost - the only one I'd consider running would be a Thudbuster. But a Thudbuster and 28s is pretty insane - the whole idea of thin tyred bike with suspension forks and posts is.

Also: that front wheel has a very low spoke count! Especially if you're a heavy rider, I'd key an eye on it - check the spokes are all roughly equally tense by pinging them; spin the wheel upside down and watch the rim to see that it is still straight.