Alternative Chain/DriveTrain DeGreasers My question is whether there is anything "special" about the Bicycle-Specific Branded Chain degreasers or whether the much cheaper alternatives are just as good.  I've used the ParkTool CB-2 (http://www.parktool.com/product/citrus-chainbrite-CB-2) but it's really expensive.  I'm wondering whether Simple Green, Purple Stuff, or any of the various Citrus Degreasers that you can get at the hardware store by the gallon are suitable.  We ride a lot in our family and I'm presently maintaining 5 bikes, so although I try to use the same "batch" each time in the chain cleaning tool, then use that to wet my brushes for the cogs, etc., it still gets pretty pricey since each bottle only gets me through about 3 cleanings.  If it matters, our two road bikes are Ultegra (circa 2003) and the others are cross/mountain bikes that see mostly road use.  I'm not dealing with offroad sludge.  The guys at my FLBS told me they really like the "real stuff," and that other cleaners might damage my drivetrain.  I know these guys pretty well and they don't usually push very hard, so I think they really believe it, but I don't know what would be "special" chemically about bike-specific products vs. the others.

I'm new here and this is my first questions, so feedback is welcome.  I did try to search first, and found a similar question (What to use to clean your chain (and cogs)?) but that doesn't really address my specific issue, I don't think.
For degreasing I don't think it's that important to use a bicycle-specific product -- any reputable "parts degreaser" from a hardware store or auto parts place should suffice.

I would recommend avoiding "do all" cleaner/degreasers that claim to wash your dishes and do your laundry as well.  Stick to a "parts degreaser" or something of that ilk.

And, of course, thoroughly wipe dry the chain after cleaning, and relube with an appropriate chain lube.  Here using a bike-specific product is somewhat more critical.