Sigma 18-50 2:8 EX DC Macro for 4/3rds

[ZenitE]

I have recently had a "present" from my partner of the above lens to replace my standard kit lens 14-45 3.5-5.6 on my E-500. ( I had been wittering on about an upgrade for months)However, I had been saving independantly for the 14-54 2.8-3.5 mkii. She didn't know this, but her Bro is a semi pro photographer so the Sigma is on his advice. I have about 200 pounds saved for the 14-54. Should i keep the Sigma or sell to get the Oly 14-54?

[Benchista]

In terms of optical quality, the Sigma would serve you very well. The constant f2.8 might be handy, too. The real concern is the limited wideangle available on 4/3 with this lens - if you can live with that, then you're laughing.

[ZenitE]

Thanks Benchista, I will keep the Sigma and put my savings toward the 9-18 Oly Optic so that one day I will have 9-18 oly, 18-50 Sigma 2.8, and 70-300 4.5 Oly.The latter 2 I already own.
At present I own an E-500, but within the next 6 months I will have saved enough to buy the E-620 and the 9-18 Oly, In your view is this a sensible combo (I am committed to 4/3rds) Love Olympus etc.