Understand your concerns about the DGL-5500. With SB, there were hoping, I presume to let SB handle any Special Application needs as I believe it was mainly be a go to for any client application and connections and would have automatically made any necessary adjustments for them on some level.
Unfortunately Qualcomm being the main developer for SB and ABE failed to fully test and maintain there development for SB thus it failed for users and this model router. Which is unfortunate and the concept seemed good and we all had high hopes for the follow on to the DGL-4500 since it was a great router and still is. So it's unfortunate that the DGL-5500 will probably not see any more FW updates as it's now gone into EOL from what I'm told and unless there is a major security flaw found, there wont be any more updates for added features like IPv6.
I personally don't use the 5500 any more and does work ok turned into a wired AP. With everyone's experiences with this model router and how it turned out, we won't be bothered if you choose to find something else. Please don't take this models as being D-Links experience on there entire router line. The DGL-5500 was a one off product that need more development time before going to market IMO which blame for this can be laid squarely at Qualcomms feet. Other D-Link routers like the DIR series have fine QoS engines and do work well for general internet and gaming. I have several. So please give the DIR series a try and review them should you like to change models. I wish I could recommend the 5500 as being a good router however my personal experience along with others can attest too, it's just not worth it. I wish things had been different and we worked hard with D-Link to correct and test issues at hand for the 5500, it just wasn't a good end game.
Let me know if you'd like a different router suggestion.
I may try loading 3rd party FW on my 5500:
http://forums.dlink.com/index.php?topic=61634.msg248146#msg248146Also for multiple gaming consoles and OPEN NAT:
http://forums.dlink.com/index.php?topic=65732.0