Option 1 is going to be costly and you may need a vendor to implement for you as that involve a bit of advance stuffs such as network load balancing and database clustering and I am not sure about your IT knowledge level. But itís not that difficult though. But anyway here is the approximate cost, actual cost could be varied.
2 web servers = 5000 S$
2 database servers = 12000 S$
External storage = I donít have that figure you need to contact to distributor but approximately 12000~15000 S$ depends on number of hard disks. You are looking at initial investment about more than 30k. But hardware last about 3 years, so you cost per year is 10K. You might want to contact some companies for leasing.
Operational cost is about 1K per month for half rack rental in major ISP, not sure abut latest pricing, so just drop them a mail and ask a quote.
Similar as option 1 but only 1 web servers and database server. With more storage space on database server, you are looking about 15K for this option plus monthly space rental in data center. It could cost you less because its only two servers but some ISP minimum rental requirement is half rack. But I am sure there are some ISPs that can offer you a space for two servers in reasonable price.
You already have figure for this option.
Now if I may suggest, you might ask contribution from soft members. A little from each will help you to move to better environment.