Rise Above Ambient Temp. (c)
	Mfg.	Model	27mm large copper block	15mm small copper block		27mm large copper block	15mm small copper block
			50W	50W		100W	100W
1	Thermal Integration	TI-V77L	12.6	17.9		31.0	37.1
2	Swiftech	MCXC370	16.9	22.0		32.1	44.3
3	Vantec	CCK-6027D	18.0	22.2		37.5	46.0
4	Thermal Integration	TI-V86-15	23.3	21.1		45.9	47.0
5	OCZ	Gladiator	12.0	26.0		29.2	49.0
6	Akasa	Silver Mountain	19.6	24.9		38.4	49.5
7	Thermal Integration	TI-S8640L	23.5	25.5		47.4	52.3
8	Swiftech	MCX370	19.7	23.8		38.0	53.3
9	AVC	112AM1	21.8	28.1		45.3	54.8
10	Thermaltake	Volcano 6cu+	13.8	28.8		32.1	57.9
11	Spire	5T060B1H3R	16.0	30.8		37.9	58.4
12	Thermalright	CB-6L	25.7	33.1		49.2	68.1
13	Fortis	A92	18.9	39.1		41.1	71.1
			50W	50W		100W	100W

We are looking at a cooler that does just about dead center results in this list of reference heatsinks.

Even though the TI-S8640L doesn't use any copper to help improve overall thermal conductivity, the heatsink is still quite good.

The taller size of the fin section and same fan bring out similar characteristics, and keep it within reasonable values for a heatsink of this style.

Although we did not specifically test this out, I have a feeling that dropping a 25mm Delta fan on top of the TI-S8640L would bring it very close to that of its copper cousin.

There is a penalty in terms of noise with this, but then again, I hear some heatsink companies (Akasa) have started to sell acoustic dampening material for cases, so you could be in luck. :)