@henry72 Thanks for the opinions! I saw your post before since I was considering the totally same configuration with yours (even now). I will go for SSD but probably for 256G only since I don't really need that much.
Also, once I bump up to the 512G SSD, the i5/580X model seems to be a more ideal option, since it offers better cost/performance value.
Glad to hear that you're very happy with your new iMac, that also gives me some confidence!
The same question here, shall I expect the i5/580X model makes a significant difference when compare with the i5/570X one for my usage?
@lishaoalox No problem at all. IMHO i5/580X is overkill for your usage. I think you should consider upgrading the SSD to 512GB, e.g. your photo library will grow over time. You can use external storage BUT it is a hassle in my opinion and it is nowhere near as fast as the internal SSD unless you get the TB3 external drive.
How long are you intending to keep this iMac for?