Well... Remember I said: if I were to buy a sub that is substantially pricier than the flagship Hsu or SVS, then I would primarily consider a sealed design. So I was talking about well over $1-2K range then. I believe that, although sealed designs have some inherent advantages (e.g., no possibility of port chuffs to start with), everything else being equal it will cost significantly more and require a larger box in order to obtain the same bass extension and max SPL as compared to ported boxes.
That said, sealed degins are definitely less tricky as an initial DIY project -- no port tuning involved, with the only relevant cabinet parameter being its volume.
With regard to the side vs. down firing configurations, I don't think they will make no significant sonic difference. It is strictly a matter of preference.
