I've only ever ordered from Attitude and only with the guarantee bc customs loves to take seeds. I've also been considering ordering from Natures Green Remedies, which I believe are domestic, so much higher chance you'll get your order and I've heard they are trust worthy. Both sites carry SinCity, along with a variety of others.
ACDC is from Sin City seeds and they also have other similar strains, Thunderstruck looks like a good option....And CW, well let's not get into pot politics for now, lol.
Using cannabis as medicine is not so much, "my doctor has heard of these strains on CNN and MSNBC so I need to use them". It's about finding what works best for you and in what form. Often higher levels of THC are more beneficial and for many using pills or edible forms is a much better and more effective option that smoking, all depending on the needs.
Both strains your asking about are primarily for very low THC and moderate CBD level. Everyone is different but I've never had luck with using CBD for straight up pain relief. For pain(back and neck muscle) the only thing that's ever worked for me is high THC cannabis concentrates. I have found however that cbd concentrates are great at relieving my muscle tension and putting me in a relaxed mood.
Also, you might wanna look at other offerings, Good Medicine from Bohdi Seeds is amazing and I've heard good things about CBD Crew and others.