A 10th or 8th scale tank all metal will cost thousands. They are out there though. rcuniverse has what is probably the most active tank forum.
All of tamiya's tanks are either 16th scale or 35th scale. An 8th scale tank would be huge and weigh a ton. An 8th scale M1A2 would be 4 feet long with the gun and 1.5 feet wide. 10th scale it would be 3.25 feet long and 1.2 feet wide.
You can pick up 16th scale chinese made tanks for around 150-200 with metal tracks, smoke, and sound all RTR.
www.matomart.com is probably the best for them. A Tamiya will cost close to 1k once fully built.
The chinese models have a ton of upgrades available for them including full metal kits and battle system upgrades.