One of the main reasons to avoid X-mart bikes is that they generally only come in one size. For someone like me who is 5'9" that's not an issue at all. For someone like you who is 6' it's starting to become a concern but you may be able to get away with it. For very tall or very short riders it's a big problem. Build quality is another problem that is hit or miss. Otherwise, a bike like that would be OK for your use.

Generally, you can pick up used X-mart bikes on Craigslist for under $50 and often they are as un-used as the day they left the store.

My current CL favorite are late 80's/early 90's mountain bikes. They can generally be had for about $120-$150 in this area. Look for something that seems not to have been ridden much and doesn't have any rust.