I saw your guide, very cool. however, I really do like the look of the wraith models, so If I do get them, I'll get the real things..most likely.
For the size and balance of the old and new models? A buddy at my store plays an all pewter necron army, and the old Immortals are quite solid. They are much bulkier then the current Immortals, but less sleek looking. I don't have any real scale relationship bettween the two, as I own no version of any immortals. Besides my lord, which is converted from one. I don't see either of them being terribly tippy, or at least from what I remember.
For destroyers, I took some pictures of one of my current ones, next to the classic one.
Keep in mind, that the older one is on an older base, therefore much higher up. For tippyness, mine are quite stable. However, I mounted my classic destroyer on a ball-and-socket joint skimmer base, so it's on it's base quite good. I also magnetized all my plastic destroyers to their bases too, so none of my destroyers are even remotely tippy. The slot on the bottom of the old destroyer is rather insignificant to keep it on a base un-glued. So you'd need to either use the old ball-socket joint bases, which can allow good storage and be quite stable. Or you should magnetize it.
For pricing, I've never seen them sold for anywhere near current value. Though, they are quite rare now, which is a factor. I am not really one to say what is the best price. Mostly, it's what ever your willing to pay, or what the seller is willing to get rid of it for. I've only really bought stuff like this off people on ebay.
Pylon out of a box? How would I help you with this? In all seriousness, the Pylon kit is among the coolest kits GW has, and for it's cost it's quite good.
