iMac Rookie here - need help with WiFi issues

Hello everyone,
I am new to the iMac and new to this forum. Trust me, I am a rookie when it comes to computers, wifi, etc. My problem seems fairly simple, but i cannot figure it out. Here's the deal.......I recently purchased a new iMac desktop. It has been connected to my wifi network through my Linksys Router (about 3 years old). My other devices (a crappy Dell laptop and both of my iPhones) have no connectivity issues. But this iMac runs SO slow. Keep in mind, I have barely any memory used. When I called the 800 number (before warranty expired), they thought the issue might be because my router was 2 floors below my iMac. So I had Comcast come in and move it up a floor (now the router is in my living room and my iMac is in the loft with an open look at it from above). Much to my dismay, this helped slightly. Now when I get online it still runs very slowly. All the wifi bars are always lit, so I think it is getting a strong signal. On my iPhone, using it right next to my iMac, a song on iTunes takes about 30 seconds to download, whereas on the iMac, it is sometimes 7 or 8 MINUTES!!! Could it be the Linksys Router is not very good when used with an iMac? Am I missing something? I could use ANY bit of advice, as I am so irritated that I paid this much for a desktop that I can't use the internet with!!! I have actually started to use my 5+ year old Dell laptop because it is light-years faster. PLEASE HELP!!!

What is the model number of the Linksys router?

Are there any other wireless devices within the vicinity of the iMac (baby monitors, cordless phone bases, intercoms, etc?).

We need to test your iMac first to see if there is a hardware problem. It's rare but it could happen. Here's what I suggest:

Move the iMac close to the router as a test and connect it via an ethernet cable. Go into System Preferences, Network, and select ethernet. Measure the connect speed with it that way. Let's see what it does. If the speed has improved considerably, unhook the ethernet cable and go wireless again within close range to the router. Again, measure the speed.

Yes, I know it's a pain to carry the iMac downstairs, but we need to make sure the hardware is working OK.

Guys, thanks so much for the quick replies!!! I will test out the connection tomorrow as CHSCAG recommended. CWA107 - the Linksys router model number is WRT160N V2.

Come to think of it, my Apple TV is connected right next to the router, and I've had a ton of slow connectivity issues with that as well. Just doesn't make sense why my Dell laptop and iPhones don't seems to be affected. Let me know what you think.