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If you plan to use no smaller than 26 tooth (for the inner chainring) and 46 for the outer chainring, then 120/80 chainrings might be best option. The SRAM 'standard' 2x10 chainrings for 120/80 are 42/28 and 39/26. Aftermarket chainrings are available in those sizes, plus 30 tooth (inner), 44, 45, and 46 tooth (outer). If you want to use smaller or larger chainrings, then 104/64 would be required. For the standard SRAM sizes, you can find chainring + spider assemblies fairly cheaply on ebay.
One difference between 120/80 and 104/64 is that 120/80 is used for double (2x10) cranks only, but 104/64 is used in both double (2x10) and triple (3x10) configurations. The double and triple 104/64 spiders are essentially the same, with the 2x10 crank mounting chainrings in the "middle" and "inner" positions, and the "outer" position can optionally be used to mount a bash ring. Most larger (42 tooth and bigger) 104 chainrings are intended to be used in the "outer" position of a triple, and the chainring holes are counterbored on the outer surface. There are a few larger chainrings specifically designed as the big chainring for a double crank (with chainring bolt holes counterbored on the inner surface), but in this case make sure any 104 chainrings labeled as "outer" are also explicitly labeled "2x10".
The one exception is that SRAM made a special 2x10 set of 104/64 chainrings in 48/32 tooth (the 32 tooth fit on the 64 BCD), but while the 32 tooth chainrings are still available, I have not found a source for the 48 tooth 2x10 chainrings. However, the 32 tooth chainring is larger in diameter than the 104 BCD, which will allow you to use a triple "outer" chainring in the "middle" position to be used in a double crank. Although the chainring bolt holes are counterbored on the wrong side and the heads of the chainring will protrude on the inner face of the chainring, the 32 tooth chainring is large enough to prevent the protruding bolts from interfering with the chain.
Also make sure any spider you get is specifically for X0/XX cranks. These will fit the profile of road cranks. X9/X7/X5 cranks are narrower, and the spiders for these cranks have a narrower inset for crankarm, and won't fit road cranks. Also make sure the spider is for GXP MTB cranks - spiders for BB30 MTB cranks have a different offset, and the chainrings will be located too far outboard.
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