The P180 is a steel case as well so it'll be pretty much just as heavy as that Silverstone. Also from what I've heard working with it is not as easy as with other cases on the market. Did you check out the TJ04 Gloria yet? It's steel/aluminum, but because of it's small footprint it shouldn't end up as heavy as either the TJ06 or the P180. I would check it out, also you can replace the 80mm fans it comes with with some beefy 120mm fans. So far these are my recommendations for you.
Silverstone TJ04 Gloria
Cooler Master ATCS, Praetorian, Wavemaster
Silverstone TJ04 Gloria
Cooler Master ATCS, Praetorian, Wavemaster