this.
also the dual to the quad is huge 2x the speed in multithread tasks with the quad. or dual a 100 minute handbrake encode low quad 50 minutes better quad 45 minutes. the big gain is the low quad take that $100 bill and buy ram.
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buying the stock quad.
http://www.macmall.com/p/Apple-Desktop-Computers/product~dpno~9418667~pdp.iadfcjg
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this ram
http://www.newegg.com/Product/Product.aspx?Item=N82E16820104257
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the rugged t-bolt 120gb
http://www.lacie.com/products/product.htm?id=10599
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this will run you just about 1045. gives you a very fast system.
yeah you can shop for a better ram deal or get 16gb ram.
you can pass on the ssd.
but the bottom line is the above system is very fast as configured.
you could argue adding the fusion drive rather then the external ssd.
if the fusion drive setup works as advertised it may be worth the 250 surcharge. but it is an unknown.