Slow wifi speed on wgr614l with dd-wrt v24preSP2 build 12533

Recently I updated my WGR614l to
dd-wrt build 12533 downloaded right from dd-wrt web site. Now my wifi speed is
about 500KB/sec, does not go up :( I tried disabling all additional services
including firewall, still no luck.

Here is my top:

root@NETGEAR:/proc/net# top

Mem: 11424K used, 1604K free, 0K shrd, 1140K buff,
4760K cached

CPU: 0.0% usr 86.6% sys 0.0% nic 13.3% idle 0.0% io
0.0% irq 0.0% sirq

Load average: 0.75 0.74 0.76 3/19 22688

PID PPID USER STAT VSZ %MEM %CPU COMMAND

3 1 root RWN 0 0.0 66.5 [ksoftirqd_CPU0]

22688 21834 root R 1176 9.0 13.3 top

1253 1 root S 2584 19.8 0.0 httpd -p 80

1282 1 root S 2560 19.6 0.0 httpd -S

14 1 root S 1500 11.5 0.0 watchdog

1 0 root S 1464 11.2 0.0 /sbin/init noinitrd

92 1 root S 1460 11.1 0.0 resetbutton

1639 1 root S 1456 11.1 0.0 wland

1268 1 root S 1456 11.1 0.0 process_monitor

1221 1 root S 1364 10.4 0.0 nas -P
/tmp/nas.wl0lan.pid -H 34954 -l br0 -i eth1 -A -m 128 -k **PASSS*** -s SOFOZ -w
4 -g 3600

21834 21746 root S 1200 9.2 0.0 -sh

21746 1 root S 1172 8.9 0.0 telnetd

21747 1 root S 808 6.1 0.0 dnsmasq
--conf-file=/tmp/dnsmasq.conf

376 1 root S 700 5.3 0.0 cron

10 1 root SW 0 0.0 0.0 [mtdblockd]

2 1 root SW 0 0.0 0.0 [keventd]

6 1 root SW 0 0.0 0.0 [kupdated]

4 1 root SW 0 0.0 0.0 [kswapd]

5 1 root SW 0 0.0 0.0 [bdflush]

 Here is my
/proc/interrupts:

root@NETGEAR:/etc/init.d# cat /proc/interrupts

CPU0

2: 1621295 MIPS eth1

3: 438 MIPS serial

4: 248299 MIPS eth0

7: 9351797 MIPS timer

What could cause high CPU load
for ksoftirqd_CPU0? Can it be somehow related to dd-wrt kernel 2.4
vs 2.6 and broadcom drivers? If yes, what dd-wrt build  can I use?

 Thanks
in advance! Have a good day!

Update 1: How about using
eko builds? Are they differ from what is linked from the router DB on dd-wrt web
site? Here is the txt and the firmware files: http://www.dd-wrt.com/dd-wrtv2/down.php?path=downloads%2Fothers%2Feko%2F...