You mean an i3 530 at about 4.1 - 4.2 GHz; coz the 4.6 GHz clockspeed you mention would be almost impossible to sustain in a stable desktop or workstation environment.
I don't know how much is MATLAB thread optimized. But it is safe to assume that, at such a high clockspeed, the i3 would be faster than the i7 860.
All right. An i3 530 at about 4.1 - 4.2 GHz also have good performance. Some people tested super-PI 1M for i3, result is under 10 second(!!).
OK. I was stupid. i7 processor that I bought last week was too expensive! Maybe i3 system is half.