Current wisdom on tighter timings versus high DRAM freq?

Until my beloved QX9650 bit the dust last week, I ran my machine w/ the posted timings, and which pretty much limited me to 408x4 or 1632Mhz w/ the DRAM I am using. Since picking up a replacement Q9650 (didn't want to change anything else out since the mainboard and memory and PSS are fine and so on--I plan on a big upgrade in about 2y) I have dabbled in DRAM Freq of 1680 w/ more relaxed timings. Seems fine, have no idea what the max I can do and still be w/in DRAM voltage etc. Still getting decent latency scores (~47ns) and better read scores so is there a good reason to go more for tighter timings or better to shoot for higher memory read scores w/ more relaxed timings etc? Haven't flown any yet w/ to test this. I had great performance previously.Noel