I've also got a similar sized home, 4800 sf or so... I have radiant heat in the floor and garage, but also use a coil in two furnaces. I have a CB6048 and go through about the same as ckbetz. And it looks like his feeding schedule is identical to mine. I hear alot about the Hardys and when I talk to people about them, I seem to hear either Hardy, Woodmaster or Central Boiler. Of course everybody loves their unit best... they spent alot of money on it and don't want to talk bad about it.
Who knows which is best....? not me.
I don't have a forced air either but it seems to me that if I did, I would go through more wood. I'm real curious about them. Not sure how they would work. Mine burns fine without it, and it seems if I left the door open, which is allowing more airflow, it would create more heat and burn the wood that much faster. Now I know that when it gets to temperature, which it would with a forced air fan, it stops blowing and I'm guessing, shuts a damper door so it smolders. I'll bet the water gets to temperature faster though with it. I just would have thought it would go through more wood. I'm assuming that's how it works and it must work well because the Hardy Boys (and girls) have about the same burn times I think.
I haven't heard anything good about stainless. Only bad. I may have missed a couple threads on this though...
On Square vs round.... I agree that there is more seams to leak. If you go with a popular brand, they should have the welding down to a science and the warranty should help. I think my CB has a 25 year corrosion warranty if I'm not mistaken. My brother has the same as mine, just the previous version of it, and is going on his 10th year with it, with zero problems. When he does replace, he said he'll go with the same.
I like the baffles inside the CB versus the Hardys. I may be wrong but I don't think the Hardys have a baffle system like the CB. It seems to me it would be more efficeint. But again... I think we all kinda have very similar burn times so I don't know....
Maybe it comes down to price, in that case I shoulda got a Hardy.
Of course the CB's are prettier...? Maybe that's where my extra money went.
Good luck!