Under what conditions would an i7 3.4ghz be advantageous compared with an i5 3.3ghz?. Is there much of a cost difference? I do not do gaming, but wish to have 4 screens with currency trading in mind. John.
For your purposes the only difference would be a slight clock speed increase and hyperthreading on the i7 (meaning it can theoretically handle twice as many simultaneous tasks).
The use cases you provide don't really require either processor, to be honest. Both are overkill. So go with the cheaper one and you will be fine. Are you using web-based currency applications or crunching numbers locally? If you are using web browsers then there isn't much going on locally and you don't need much hardware to do what you want.
Also, any AMD graphics card that supports Eyefinity can handle your needs. You don't need a high end card since you aren't pushing any graphically tasking programs.