If you really want some US silver dollars, I would recommend you search around and buy a few really nice ones graded by PCGS or NGC (MS63 or higher), and spend the rest of your investment $$$$$ in 90% halves that are not highly circulated (late year Franklins are the best since you don't have to worry about any dates being less than 90%, vs. the Kennedy halves). This is assuming you get halves for the same price as quarters and dimes, which I can get locally although I don't buy junk silver anymore since I can get .999 for about the same premiums.
Every category of US silver dollars are overpriced as far as bullion investing goes. Even the cull/damaged ones here sell for about 1 dollar per ounce higher than good condition halves, quarters, etc. For some reason people like the old silver dollars, even the crappy ones. Also, there is a higher risk of counterfeit in US silver dollars than any other US silver coin from what I have read, although that risk is probably not too great if you buy from a reputable dealer (be careful if buying on online auctions, etc).
I believe one day if/when silver prices get really high, coin dealers will start buying and selling junk silver by weight and not face value. That would make less circulated coins worth more than highly worn ones (like Walkers and most quarters and dimes). Some say the old, worn Walkers will have some numismatic value someday and I agree, maybe in 2050 or later--of course if you can get nice ones for the same price as regular junk coins get those. For this bull market I would avoid the worn down stuff if you can get less circulated for the same price. The 1964 Kennedy halves probably represent the best value weight to price wise, you just have to always check to make sure some 40%ers weren't thrown in the pile when you buy them. That is why I always bought the later year Franklins that didn't show much wear.
Just my opinion.
Jim