Flash or new Lens for Piano recital in side a church?

[m500]

I got less then 3 weeks to decide if I need to get a flash with my current lens line up or get a new lens for the occasion? I'm having a hard time to decide. Originally I was going to bite the bullet and purchase 70-200 f2.8is but its just too heavy and I'm not sure how many times I will actually use it. It seem a waste of money for something that just sit in the shelf 360 days of the year out of 365 days. Also, I need to save for the raining days for the clasping economic more then ever now. Any suggestions will be welcome! Thanks.

My current ideas:

(1) Get 580ex II with my EF 28-135, Tamron 17-50 f2.8 and EF 50 f1.8II
or
(2) Get 50 F1.4 & 85 F1.8

[FlyingPhotog]

How about renting a 70-200mm f/2.8L IS?

[lungdoc]

I'd go with flash if it's allowed. Consider 430EX as significant cost and weight savings and it will serve most uses very well, can be a slave if you ever need more.

[Dan-o]

I would also get a flash if you can use it there. If you did have a 70-200 you would use it a lot more then you think.

[Mike]

I think a flash may be a bit too intrusive at something like that. I vote for fast glass.

[PhotosGuy]

Depends on what you need the pics for, just how crappy the light there will be, & how close you can get, doesn't it?
With fairly even light (no black holes in the eye sockets) I'd try the 50 f/1.8, wide open.
I have the 85 f/1.8 & used it here at ISO 1600, SLHS V-ball tournament (http://photography-on-the.net/forum/showthread.php?t=594045), but the light was spread around in the gym.

Have you been there before? Do they have a dress rehearsal the day before?

Otherwise, the cheapest, & probably best option would be to get a flash & learn how to use it.