How much memory load are we talking about here?
DNN in it's own application pool uses lots of memory. it loads almost all .NET dll's sindce it uses all technology supported by .NET. I consider 100 megs as normal on a non caching DNN site. 150 megs when an admin logs in and does alot of admin stuff.
the article you link to talks about 500.000 pages? if they all cache 1K thats 500 megs of cache. 1K is easier to reach then you think, and then we aren't even counting the cache for the subsystem. (reflection cache, membership + profiel data, ...)
SQL server uses lot's of RAM but it seems to be verry friendly in giving it back to the system for other software, there is latency offcoarse
My experience says, an opteron with a whole lot of memory as a dedicated webserver is alot cheaper then a quad itanium to make up for not caching. so I put my large DNN projects on dedicated servers with 4 gigs of ram and the caching set as high as possible. (a day for static modules, heavy caching and custom modules cache *everything* that comes from the DB)
going dedicated might be worth the investment, at the verry least you will have acces to the eventlog + WMI to monitor DNN behavior yourself