the first thing I would do is speed test your connection
with this information you would then know what to expect out of a slingbox
If you get 256 kps upload speed than I don't care what connection you have on the other end or router the picture will be marginal at best when remote viewing

Now if you have 1000kps up then you can start to take other things into consideration

for me I have a 15mps down and 5mps upload so I can worry about other things

As far routers go
the best router is the one that works and does what you need it to do
I love my wrt54gs but it has a problem that won't let me watch my slingbox in LAN mode. I can view using my IP address but then I'm like remote viewing in my house and don't have the benefits of LAN viewing (very high kps).

I do FTA installs and use 39 dollar netgear routers for people that want slingboxes. They don't have the the range as the linksys but I never not once had an issue with them. So in a sense they are very good routers. They configure usually automatically so you most of the time don't even have to worry about port forwarding (that's open a port in the router to allow incoming trafic to the slingbox)

The question about what router protocol to use is more personal than anything else. I don't know anyone streaming at 20,000kps with an N router. The fastest I've seen one of these babys stream is 4000kps and you can do that on a G or N.

I've tried every N router out there and none of then match the distance of my wrt54gs and for me that's a very important factor

I guess you need to find out what's important for you and then take the leap of faith

r

Even a very inexpensive wireless router will be able to handle a slingbox stream fairly well. Wireless is very finicky, and you'll get much more benefit from things like repositioning the antenna(s) slightly in most cases. Unless you're doing multiple HD streams, even plain 'ol 802.11b/g will be more than enough.

802.11a is not very popular, and the higher frequency means lower range.
802.11n is still iffy unless the vendor personally vouches that two peices of equipment are compatible (and won't interfere with a third)

As for upload speed (for off-site viewing), almost any router will be able to handle it.

If you have other people at home using the connection for other things (voice, browsing), then look for something with QoS. If not then don't lose sleep over it.