too lazy to look for any benchmarks but I believe the E8xxx series were about 15-20% faster clock for clock then the E6xxx.
Wrong, it was 10-15% faster in average than Conroe. But in a per clock cycle, 5% is usually the average number.
http://www.xbitlabs.com/articles/cpu/display/intel-wolfdale_13.html#sect0
Well, everything seems pretty clear. Summing up everything we have just said, we can state that new dual-core Core 2 Duo E8500, E8400 and E8200 processors on 45nm cores are great from all stand points. They are faster than their predecessors working at the same clock speeds. Besides, their working frequencies are initially higher than those of previous Core 2 Duo CPUs. And taking into account that Intel is going to sell the new solutions for the price of Core 2 Duo E6850, E6750 and E6550, we can all get free performance improvement of 10-15% on new Intel dual-core CPUs.
http://www.anandtech.com/showdoc.aspx?i=3069&p=3
Let's point out the zeros first: SYSMark, iTunes and Oblivion all showed no performance increase from Conroe to Wolfdale. Not all applications will benefit dramatically from the improved cache or architectural improvements and these are examples of some.
The DivX 6.6 test shows a particularly impressive 10.5% increase in performance, especially when you keep in mind that we are running the same DivX test we always run and not an SSE4 optimized benchmark. If you'll remember back to our Intel-sanctioned Penryn preview, with SSE4 enabled Penryn's DivX performance skyrocketed. But this test here shows us that even without SSE4 optimizations, Wolfdale is a healthy 10% faster than Conroe. Windows Media Encoder 9 saw a 5.4% increase in performance, which is still tangible.
Wolfdale also seems to do quite well in 3D rendering apps, giving us 6.7% better performance in 3dsmax 9 and a similar boost in Lightwave. Cinebench performance improved even further at 9.1%.
Gaming performance is a bit of a mixed bag; we saw everything from Oblivion's 0.4% performance improvement to 8.5% under Lost Planet. Wolfdale is good for gaming, but the degree is very title dependent.
On average, Wolfdale ends up being just under 5% faster clock-for-clock than Conroe. Definitely not an earth shattering improvement, but an improvement nonetheless. Focusing in on specific benchmarks, Wolfdale can look even more impressive. Without taking SSE4 performance into account as we don't know how widespread SSE4 applications will be upon its arrival, Wolfdale will simply make competing more difficult for AMD's Phenom, but not impossible.
But I can tell you that SSE4 improves greatly the video encoding performance.