I occasionally use the Yaesu FT-817nd on my SOTA expeditions if I want to use higher bands on the activation or for some odd reason want to operate SSB:-). I actually prefer it to the KX3 simply because it is less bulky and it performs well in the field. One of the concerns I have with taking the 817 is; should I take an external power supply since the internal, rechargable, battery can have a relatively short life span. This is due to the power required to operate the 817 versus smaller, CW only radios. I was looking for a higher capacity battery made for the 817 and came across an interesting offering on EBay. The link is http://www.ebay.com/itm/3000mAh-Polymer-Lithium-Battery-pack-back-door-holder-Yaesu-FT-817-ND-radio-/331093734430?pt=US_Radio_Comm_Antennas&hash=item4d16b9741e#ht_4797wt_706
The product is a 3000mAh LiPo battery that fits the 817, a replacement for the battery door that allows the battery to be charged by an external charger (included) and a nice stand for the radio. (The battery that comes with the 817 is 1400mAh) All this for $89. Now, it is a product made in China, so it is tough to determine quality, (that's also true for certain US producers as well). I ordered the package and will test it to see if it is as advertised. W4RT offers a similar product but it's priced at $150.00 and the battery is a NiMH.
I have no commercial interest in this product, but it seems worth the money if it delivers as advertised.