If you aren't wedded to the window on the top (and the current hole would prevent you from mounting a radiator) you can get a new top panel at SilverPCs for about $25 (I'd have provided a link, but the link option was giving strange results and I'm out of practice writing HTML). If you don't have a giant hole in the top now, a "regular" grill should cover it.
Here's a pic of a Thermochill 120.2 in my PC-61. You would loose the top two 5.25 bays, but you wouldn't loose any PCI slots. I guess you'll need to think about the trade-off. Oh, and the grill is "square" with respect to the top, it's just a funky pic and I'm too lazy to take another
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Edit: One thing to consider when putting the radiator on the top is the amount of space between the radiator and the PSU. I've got a Silverstone Zeus 520 in this box and there can't be much more than half an inch clearance between the radiator and PSU so you may have to be rather precise in mounting the radiator depending on the PSU you're using. If you'd like a pic of the clearance, let me know and I'll post one in a separate message (multiple pics show up as links if they're in the same message and I'd rather the pic show up with the post--and I upload the pics (rather than linking to my server) since I hate looking at old threads where the pics have disappeared, so I'm making sure mine stay with the thread).