No, I personally don't think the question is on-topic.
What is our site's purpose? To quote the FAQ:
Crypto Stack Exchange is for software developers, mathematicians and
others interested in cryptography.
Cryptography Stack Exchange is for asking questions about the
mathematics and properties of cryptographic systems, their analysis
("cryptanalysis") and subsidiary topics that generally make up
cryptology, such as random number generation. As such, we welcome
questions on topics such as:
- Asymmetric and symmetric cryptographic algorithms.
- Cryptographic protocols.
- Cryptanalysis techniques.
- Hash functions, hashing.
- Entropy and information theory.
- Random number generation.
I don't think the question fits the topics presented here at all; the best fit might be "about the mathematics and properties of cryptographic systems". The issue for me is the lack of cryptographic knowledge required to answer the question. In essence, one might as well ask "if I want to buy a graphics card that is fast at integer computation which uses a lot of memory, what should I look for?" That is, it is possible to (easily!) remove all cryptography from the question entirely without changing the answers in the slightest.
More generally, one might ask "what makes a graphics card fast, ignoring floating-point arithmetic?" I can't imagine a cryptographer being terribly interested in the question, at least not from a cryptographic point of view, and that's the crowd we are trying to appeal to.
That's not to say that hardware is off-topic in general. As you've pointed out, hardware performance is a major design goal. But hardware questions should be focused in such a way that something from cryptography plays a central role. For example, a question like "why does Serpent perform poorly in software but pretty good in hardware?" seems fine to me, if a bit broad.
To sum up my thoughts on the matter, if the hardware question is somehow related to the design of primitives or protocols, I am fine with it. As another example, I think "how does scrypt use a lot of memory" might be an on-topic question (although not a stellar question in its own right).
All-in-all, I think the question was much better suited for the Bitcoin SE.