1. DSLR: it was found that 400D is not very nice for astrophotography, what I mean is, it's good, but it's not as good as 300D/350D. It really makes me re-think my plan entirely, maybe it's better to buy a 2nd hand 300D/350D and use it exclusively with my Borg 45ED II plus some cheap lens like 50mm f/1.8 and forget about daily usages.
However, given the fact that I ain't going to do very long exposure with my TG-SP II, maybe it's sufficient? Say 200mm f/2.8 at around 3 minutes. I don't know.
2. Visual: just read an article in S&T, someone suggested that 5" refractor at around 20x is about the best stuff for visual observations, sounds like a Borg 125ED is still on my dream list.