I see that this post is a few days old, so I hope I'm not too late to offer advice. As the other responder said, the 4006 is an excellent switch if certain conditions are met. If all your wire aggregates in one location with very little possiblity of you expanding into other closets, than for a budget minded network, the 4006 will admirably perform all your needs. I would submit, however, that if you are only sending ip data packets with no chance of expanding into Voice or Video over IP, or frankly any other "wierd" services, the supervisor three engine is probably serious overkill. The supervisor 2 should do anything and everything you need. Also with the 4006, the chasis gives you a lot of flexibility to grow and change. Now, the 4006 is still pretty pricey for a lot of SMB's, so let's talk about your choice of the 3550's. The 3550's are also a great line of switches, and considerably cheaper than the 4003/6 chasis bad-boys. You can get the 3550's with the capability to perform dynamic ip routing, which *may* be able to save you from having to buy a router, depending on a variety of factors at your site. Without knowing a lot more about your network, it's hard to say exactly what is right for you, but I'll give you some of the "rules of thumb" that I use when buying switches, and I buy *a lot* of switches.......
Count up the number of ports you know you will use and think you might use in the future, then add 10% to that for even more future expansion. Then round up and buy the biggest model of the family that you choose.. For example, if I know that one wiring closet contains 70 drops, and might get five more in the near future, I have a need of 75 drops. I add ten percent to get a total of 83 drops. I won't buy anything less than eighty-three switch ports when I go to purchase for this closet. Let's say I've settled on the 3500 series of switch for this closet. I could get eighty-four drops out of buying one 3548, one 3524, and one 3512. I wouldn't do that, however, instead I'd buy two 3548's for a total of 96 ports. Why? For one, the price per port is cheaper the more you get per switch. Considerably cheaper. Yes, a 3512 costs a lot less than a 3548, but when you divide the price by the number of ports you are getting, the difference is amazing. Second, in order to stack those switches you are either going to use cross-over cables, which will take up some of your precious ports, or you are going to buy giga-stack modules. Two switches requires you to buy two, three switches would require you to buy three, bringing the total price much closer to the price of two 3548's. Then, if you are wise, you will purchase SmartNet on all this equipment, meaning again that you will purchase three seperate maintenance agreements instead of two. You may even end up paying more for 84 ports, then you do for 96, depending on your vendor.
When you select a vendor, look for a silver or gold Cisco partner, rather than just a re-seller, or premiere partner. The gold and silver partners get their equipment at a much, much, much larger discount than a plain old reseller, and will usually give you much better pricing. In most parts of the U.S. the local phone company is often a gold/silver partner, but at least in my area, they will only beat the "mom-and-pop" resellers and will still mark up a very high margin compared to what they get the equipment for. Shop around, if you don't require an engineer to install the equipment for you, find a good vendor who will give you a good price and have the equipment drop shipped to you, they don't need to be right down the street.
If you are running a pretty basic client/server type of network that isn't doing anything "unusual" or particularly intensive, ie. Users print and file share, and go to the internet, then don't let yourself be oversold. If you are doing bandwidth intensive apps across the wire that need Quality of Service assurance, video capability, whatever....then definately buy the high end stuff. If you are just sending IP between Win9x machines and and NT or NetWare server for admin files, a stack of 2900's will probably fill all your needs. Simple switching is layer two, if all you need is a switch, just get a switch. Don't buy into the QoS, L3, VOIP, flux-capacitor, 1.21 gigawatt, travels-through-time at 88 mph stuff if you don't need it.
Lastly, leave yourself room to grow. There is a lot of rack-mounted inline stuff coming out these days, for everything from in line virus detection to bandwidth management that will turn the head of the boss one day. Make sure you have switch ports to plug into when (s)he has a case of shiny new toy syndrome and you need to integrate it into your network.
Enough of the rant, that's my two cents, for what it's worth,,,,, Good luck
