Hi again Jodee, I would err on the side of the slightly more expensive brands or at least those that show the active ingredient of what you are taking on the label. Those that are v cheap usually are for a reason. As far as echinacea goes I'd expect to pay £5-7 for a month's supply, the Hoefel's ones are about 6.50 and you can get them everywhere (ie supermarkets) Bioforce is also a trusted make. If you have a small and friendly health food shop nearby you should pester the assistants to tell you the difference in all the brands they stock, they will know...
Curious to know the facts on ginseng Enid, like I said I'd only just read an article on it which omitted any downside...
Another thing you might want to try especially for the sex drive aspect is using amino acids supplements to boost your brain's own chemicals. I got into this over the summer and I swear it has helped me so much. I was feeling terrible for well over 2 months and with balancing the right nutrition (yes, boring veg I know!) and using the aminos - it definitely helped. I felt fantastic by the end of the course. Its good as you don't need to continually take them, just until your brain's 'boosted' back up to its original levels that get depleted in stressful times. I would certainly use them again if I had cause (probably after xmas no doubt!) Its a long explanation to work out which amino's are best suited to you. So I would suggest running to the library and getting a copy of either 'The amino revolution' (can't remember author, sorry) or 'The diet cure' - by Julia Ross - the 2nd being my personal favourite as its less scientific and really shows how what you put in your body can affect the way it works...
Sorry if this info is surplus to requirements but I wouldn't have believed it myself if someone hadn't recommended it to me - and yes, there are specific amino's you can use to aid your sex drive, but you also have to look at the complete picture.
Once again, good luck Jodee