I do not know how you would be able to do this w/o alienating your advertising base, but you my want to start setting up some "recipies" for machines in your collection here.
Sites like SharkeyExtreme have been doing a smaller version of this, with three different setups (Bargain, high end and Extreme) posted each month.
They outline suggested power supplies, cases, coolers, chips, memory, everything (even OS).
This might be useful here as well, but maybe more along the lines of different box categories as well as $$.
Low Power consumption (either running or idle)
Just start asking or looking around to see what kinds of machines people want to build, then group them up by that and try to break it down a bit by price. But the key here is that each area should have a complete grocery list of what you would need to build, and have a working system.
Now, one step further than Sharky would be to take these machines and stack them up on a composite chart, listing their title (MONSTER performer, Stealth box, LAN box, whatever), what pieces and accessories they have, their relative price (with a date for when the price was computed) and, most importantly, some stats on their performance!
That way you get a full roadmap for each, a price guide, a performance guide all in one.
Making the machines clickable for further details and possible comments would make for readers to make suggestions for the next model to be featured.