there are so many issues to work on but for some reason every rehdat or clone i have ever tried has run horribly....

you really have to get the smaller more optimized kernel compiled
trim everything useless out of the config
you have to edit the Makefile and add -O3 -march=athlon
flags
your choices are
athlon, athlon-tbird
AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions support.
athlon-4, athlon-xp, athlon-mp
Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE instruction set support.
k8, opteron, athlon64, athlon-fx
AMD K8 core based CPUs with x86-64 instruction set support. (This supersets MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.)

whatever you have there

put these flags in the kernel Makefile variable
HOSTCFLAGS
HOSTCXXFLAGS
and
CFLAGS_KERNEL

next cut out all the cruft from the run level boot so you are not running services like crond and http and ftpd and whatnot you don't want or need (look up all the services you are running and decide if you need them) test by killing them off and see if everything still works

next you can play with your video bus latency settings
run
lspci -v
and you find the name on left for your components (something like 01:00.0)
try
setpci -v -s <video device name> latency_timer=ff
this sets video burst size to max
you can also set the main bridge to like latency_timer=b0
or something and see if it helps

Missed that, sorry.

Do you have the specs for your video card and monitor? If so, try running xorgconfig, it'll help you, well, config xorg!