See:
https://wiki.mobileread.com/wiki/E-book_Reader_Matrix
for a detailed comparison.
I'm partial to to my Kindle2, but that seems to be a poor option since you already have 'heaps' of books without needing access to a store and since you live in Singapore. The next choice would probably be Sony, but again the strength of Kindle2/Sony are partly based on their excellent book stores. So, if you don't need access to specific stores, I look towards cheap.
The two cheap choices, in the US, are the Jetbook and the Astak EzReader. I'm not sure what happens with costs/shipping to Singapore. You'd have to look into that. The Jetbook isn't an eInk device, but it is (was?) on sale for $169 at newegg and the current owners seem to really like it. The Astak EzReader is the Hanlin under the Astak name. It has been on sale for $229 at Fry's but I don't know what the current price is. Search for EzReader. If these folks don't ship to Singapore, then I don't know about prices there.
Most eInk readers (except for Amazon/Kindle) are manufactured by Hanlin or Netronix. In general, I have read some good things on these forums about Hanlin. However, many of the comments seem to be based on the spec's not on actual user experiences. The other major manufacturer is Netronix and they make many of the other readers out there. I had an early generation Netronix reader, the Cybook, and wasn't too pleased. The button pushes required were a bit too firm. It wasn't clear if this was Netronix's fault or the Cybook software. More recent users have given the Cybook better marks.
Regarding the Irex devices. My second hand impression is not that positive. It appears that they win the spec war in many cases. You can order a larger screen + touch screen + .... However, it doesn't appear that the actual user experience is really that smooth. I'm not convinced eInk is ready for those features yet in terms of durability and response speed. Furthermore, the prices are clearly a premium.