They are both slightly below 500MB each and so can be installed together. BTW, the Chick"s one is only Rhodes samples, whereas Purgatory Creek contains Wurlitzer, Clavinet and Pianet samples. If they offered only the Rhodes samples (two types AFAIK) it would have been 200MB and cheaper. I personally don"t care about the other samples, I"m interested only in Rhodes sound, so it"s a bit of waste for me which is another reason to be hesitant. They both sound very pleasant to my ears. But I still have a slight preference towards Chick. Also because I loved the guy and have grown up listening to many of his records and his Rhodes piano.
P.S. Sorry I misread your question, I thought you were asking about installing both Chick and PC Rhodes. To your question, yes, it"s exactly what I have on my MODX: the Bosendorfer and Chick Cores Rhodes and there"s 80-90 MB free space left if I remember correctly.