You can definitely stack SARMS with AAS, and there is no problem at all with that. In fact, SARMS are always a great addition to a cycle, since they will give additional benefits without any side effects of their own. If you will stack Test+EQ+Cardarine you would be getting the ultimate endurance stack that can't be compared with anything else.
As for the HCG, I would not use it, neither on cycle, nor off cycle, since its benefits are definitely not worth all the risks. It can cause such side effects as gyno and suppression, and it will barely do anything for your natural testosterone production. In fact, it only mimics the functions of LH and FSH, but it will not actually make them work. As a result, you will get an increased level of testosterone only while you take HCG, which will drop back down as soon as you stop using it. Therefore, it would make sense to use something that will cause less side effects and actually do something for your natural testosterone production. For instance, you can use HCGenerate ES - it will keep the plums big and functioning during the cycle, and it will be a great help for natural testosterone production during PCT, since it will make LH and FSH actually work. As a result, your body will keep producing testosterone even after you stop taking it. However, unlike HCG, it will not cause any side effects at all, and it is more convenient, since it is taken orally. Besides, the libido boost from HCGenerate ES is a sight to see.
Regarding the possible sources to get your stuff, I would recommend you to visit the source section of EVO (
http://www.evolutionary.org/forums/source-talk/). There you will find detailed information about different sources, and will see feedback from their customers. I am sure that after doing a little research there you will be able to make a well informed decision in regards to the source for your gear. Personally, I love the Berd Pharmaceutical stuff sold by Roidmass, but you should never listen to just one opinion, and do your research. The above mentioned place is a good place to start.