Which bike do you ride on mild offroad tracks that gives you the desired comfort? Of rigid bikes you're left with MTBs I guess?
That is what I was looking for when I tried out the Pinnacle Lithium. I found my Brompton more comfy than my Btwin 520 on the rough sections of the Leeds-Liverpool canal towpath when I was working in Leeds last year. I guess that gravel/adventure/wider tyred touring bikes should be ideal on rough paths and forest roads but I haven't tried one yet but I am a bit suspicious of the advertising hype. FWIW I am currently musing over the suitability of the Genesis Longitude and Surly Disc Trucker for rough stuff touring but they are quite a bit more expensive than Lithiums especially if the OP can get a 50% discount!
I accept 531colin's point that better tyres should/could improve the ride quality of the Lithium but if so, why doesn't Evans fit them? ...To meet a price point I assume.