The Steelhead is compromised by its own very mediocre output coupling capacitors. And if you use it as a full function preamplifier, then the signal has to traverse two of those same mediocre capacitors. Upgrade the capacitors, then you've got something.
Any turntable that is not internally suspended (aka "isolated") can be isolated by placing it on an isolation device, at extra cost, of course. On the other hand, it is not wise to place a suspended turntable on an isolation device without understanding what you're doing in great detail. The two different suspensions may interact with each other, badly. Since devices like the Minus K or Vibraplane are generally superior to any built-in type of suspension commonly found in commercially available turntables (with the exception of the Dohmann Helix, which uses Minus K), I prefer external isolation devices.