I'm no expert but that 4GB of RAM should be plenty for any 64 bit version, eg Vista or Windows 7. I always say the more RAM the better, but there comes a time when that extra RAM is just unused. I don't see many applications needing anything like 4GB of RAM.
Photoshop Essentials may be RAM intensive, (I haven't used it for some time so I can't be sure), but I doubt iTunes is. CorelDraw may also be intensive. I assume it depends what use you put those apps to.
What is the graphics card on a Dell Latitude E6500 like? If it uses shared memory, (with system RAM), then perhaps that could be less effective than if the video card had it's own memory, like 512MB or similar. Win 7 Pro will be video extensive with it's Aero options and a card with it's own memory would be better. But I don't know how easy it is to change those cards in a laptop.
IE and Firefox work well in 64 bit versions. I have both in my Vista Ultimate 64 bit and have had no difficulties.
XP Mode needs Win 7 Pro or Ultimate anyway, so if you intend to use it you will need the Win 7 Pro version.
Compatibility is always a question on upgrades. Microsoft has it's own Compatibility checker to check the hardware, but there is often the odd application that fails in the new OS. Those drivers you have will have to be Win 7 drivers of course.
Mark
Not to beat a dead horse, but I will try and keep in concise.
I'm going from XP Pro to an Upgrade of Windows 7 Pro. My system is a Dell Latitude E6500, Core 2 Duo P8600 2.4 GHz, currently showing 3.48 GB RAM (4 physically installed). Most RAM intensive program is PS Elements 7 and iTunes, though I'm thinking about Coreldraw 5. Maybe run XP Mode.
Is there enough speed increase due to small amount of RAM "seen" by 64 bit to install Win7 64 vs possible hassels of any incompatibility? All the drivers I need seem to be available, but do the 64 bit version of things like IE7 and Firefox have more trouble than 32 bit versions? Am I missing anything?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic