Your current case, the CM690 is a midtower, it's not a small mid tower, yet still a midtower.
Without swapiing motherboard to a mATX or simular you'll not really get a much smaller case.
By removeing a load of drive bays and fitting the psu in the front Lian-Li have shaved off a chunk of the total volume.
The Panzorbox is very nice but by moving bits around NZXT didn't reduce the volume that much, what lost on height is made up by extra width.
If your specs are correct and you have a Xigmatek s963 cooler then that actually an advantage as it'll fit in a narrower case than a 120mm fan based tower cooler.
You could look at the Casecom 6788, not much smaller but it is lighter.
http://www.ebuyer.com/product/172779
I'll drop mine on the scales tomorrow to see what the total is if you want.
The other one I'd consider is this extra value one
http://www.ebuyer.com/product/150284
http://image.ebuyer.com/UK/P200-0150284-07.jpg
As you can see it uses a front PSU like the Lian-Li, so like the Lian-li it's a bit longer in length, but shorter in height, also it's narrower.
Being a cheap case, this is going to be thin steel and plastic, so the quality will not be great however it will be light weight.
Only has 80mm fan slots at the back but with the layout there should be plenty of room to fit a 120mm or 140mm fan at the top, probably two, If you don't mind modding a case.
I'd also check the weight of your PSU, PSU tend to be the heaviest thing inside a case.
Cheap PSU's tend to use low grade components that are far lighter, reduceing the weight of the PSU, but that would be asking for trouble.
However getting a lower wattage PSU that could still cope would probably reduce the total.
Question, have you pulged your pc into one of the power monitor things? if you knew what you're pulling under load you'd have a better idea to what you could get away with.
I'm thinking the Corsair CX400w would probably be able to cope with an overclocked c2d and 4850.
Oh and the miniP180 is a very nice mATX case, however it's not small, it's the size of most normal mid-tower cases and it's very heavy.