I agree with both Sting and Yanche about the size of the pipe, BUT from a practical standpoint, the 1" pipe is more than adequate.. The upgrade of the circulator pump to push hot water through a 1" pipe compared to a 1.25" or 1.5" pipe is minor, in fact if you want to push the higher volume through a larger pipe you would need to upgrade the circulator pump for the larger pipe, just like you upgrade the circulator for the higher 'head' or flow resistance through the 1"pipe.
A standard cartridge pump burns about .8 amps.. these are rated at 1/25 hp.[Taco 007,Grundfoss 15-42etc] The next size up burns 1.7 Amps, and is rated at 1/12 HP..[Taco 0011, Grundfoss 26-96] I have absolutely no problems pushing ~160K BTU through a 1" Pex-al-Pex pipe with the 1/12HP pump. My pipe runs are 150' long.
The cost of larger Pex pipe is prohibitive, as is the cost of Copper, and the inflexiblilty and potential leaks of iron pipe and pipe joints.. The vast majority of outdoor wood boilers and remote heat units use 1" Pex-al-Pex, for it's strength and Oxygen barrier.
If you have decided on the BTU capacity of an S130 or similar output boiler, you will do fine with 1" pex-al-pex.. 1.25" Pex is available, but is not available in Pex-al-Pex.. this is important and the additional cost is about double..
For about $5 per month extra electricity, I just use a more capable pump.. works great.. The cost of the pump over a 'standard' pump is also minimal.
And the debate goes on..