Elmo just sent me a link to this thread.
I have been a bike guy for years.. and have worked in shops the last 26 years. As has been said.. for a full suspension mountain bike.. you will need to pay more than $500.00 [for anything worth owning] .
As has been said a hybrid would be a good option. With the way your back sounds.. It does not sound like you will be mountain biking.. meaning riding on rough trails. In general hybrids will give you a more upright posture.. than a mountain.. but it really depends on the bike...so don't just rule out a lower end mountain bike.
Not knowing what is wrong with your back... it's hard to recommend. but sitting straight up right.. is more jarring on the back, than leaning over more. All the shock goes straight up the spine. Leaning over some can be less jarring. For those that are healthy.. and limber.. a properly fitted road bike.. can be more comfortable than any of the others [although I am not suggesting this as an option for you].
For just protection from Jarring.. suspension seat posts work well. Some bikes come with them.. and there are plenty of after market ones... with of course different qualities. If you find a bike you like [that fits] and the post is not as plush as you would like.. most shops would swap it our for a better one.
I would recommend you find a shop you are comfortable with. Proper fit is important.. esp. if you have problems. New bikes also adjustments when new... adjusting cable stretch and that type of thing. Shops usually do that for free.. and most often while you wait.
The bikes direct stuff is not good. If they have to tell you how good a deal their stuff is.. then it probably isn't. We get them into the shop all the time... brand new they need a bit of work.
Motobecane is not the company it once was.. neither is Schwinn... or mongoose. They are just names that someone bought.
For example Schwinn went bankrupt and just sold stuff off.. the name has perceived value. but now the bikes are just department store quality [or lack of]
I won't recommend one brand over another though.. as long as you are dealing with a decent shop.
For example you may be looking at Specialized and Treks... in a particular type of bike you are looking at.. at a given price range.. one might fit you better than another. In this example Trek is not better than Specialized. There are differences... and you may like one better than another... and You may find at a given price.. one might give you a better value. than the other.. but at a different price point.. that could swing the other way... just don't limit your options by brand up front.
At the shop we will go through the lines that we carrry and look at that. In some cases we choose on color.. we will think these colors are more sellable [for our market] than those colors. [yet we can also order any of the other we chose not to stock]
Recumbents.. for some backs they can be better for others not. I have seen some hurt their back riding recumbents. Most of them will take longer to get comfortable on. Meaning they can be harder to ride [to start with].. the balance and technique is different.
good luck
