I have towers and love the way towers look and sound. But in all reality if you are running a sub or 2 and xover your speakers at 80hz you really just need speakers that have a -3db point lower than 80hz. However if you have the budget and room for towers by all means go for it, cuz I'm under the opinion that bookshelves really aren't that much cheaper than towers if you have to buy stands to put them on.
Not saying you should buy exactly what I have but I would take a look at the speakers and subs just to see what you think.
I have BIC Acoustech 2 - PL-89 towers, 1 - PL-28 center, and 4 - PL-66 surrounds and I have 2 - Outlaw Audio LFM-1 Plus subwoofers. I think the system sounds great and its hard to beat for the price. I paid under $2k for my 7.2 speakers and subs.