No -
There's no 'magic potion' to somehow make your eMac perform at the level of even the slowest intel mac.
The best that you can do is the normal system maintenance - much of this is done by OS X itself.
A hard drive with plenty of free space for your OS X system to work. Free space should be at least 25% of hard drive capacity.
Max out your RAM memory.
Don't load down your OS X system with software that runs in the background, unless that's part of the software that you use. One of the worst offenders is any anti-virus software.
Don't get sucked in by something like MacKeeper - that's one that you see banner ads all over the net. Makes you leaner and meaner (You would be leaner and meaner, not your Mac. Leaner because you wasted your money, and meaner because MK 'helped' you by trashing your system

)
Tech Tool Pro is good at what it does, but it's not the 'ultimate super-speed-make-my-Mac-blindingly-fast-and-trouble-free' tool that you might want (there isn't one of those), but it CAN help you decide how to proceed if you are having problems, and can help you keep your Mac at whatever its best level is.
Most Mac users would have OnyX close to the top of any maintenance utility list. Other users will offer the opinion that you really don't need 'other' software, when OS X does a pretty good job of maintaining itself. I'm somewhere in the middle, I think.