i have the pc60 and sometimes i think that i shouldve gotten the pc70 due to the extra room inside. the extra room would be particularly helpful in your situation since you are going for water cooling.
the case itself, i am sure it is solid. my pc60 has been probably the best case i have ever worked with (i have worked on over 20 computer systems and cases ranging from the antec sonata to a chieftec to a thermaltake xaserIII to raidmax cases to no name brand cases... etc...). awesome build and it looks mighty nicer in person too.
another thing, i have modded mine quite a lot... you can see it in my gallery below.
there is absolutely no reason why you shouldnt mod the pc70... it is made of aluminum and with the right add-ons and color combinations... it is easily modded. you should let the 190$ aspect of the case hinder your creativity. CHECK MINE OUT FOR IDEAS!