Dear ah tong,
If you are going to get a Canon Digital SLR camera, most of your accessories will be compatible with your new digital camera. Lenses are definitely ok, flashes with EX designation will have no problems with E-TTL metering. EZ flash will not be about to exploit E-TTL function. But if you don't uses these, then it does not matter anyway. Exactly what lenses/accessories do you have? Perhaps we can help you better if you are more specific.
Only the Canon 300D comes with a kit set including lenses (EF-S 18-55 mm). The Canon 10D/1D MK II/1Ds are all sold without lenses. Some shops may still carry Canon D30/D60/1D, which are all obsolete models, but still great cameras. You may not have a lens that is as wide as the 18 mm on the 300D kit set. If you are on a budget, this is the set you should consider, bearing in mind the 1.6X magnification factor. For less than S$1800, your new camera will have a lens with an effective wide angle of 28.8 mm.
I do know that one of the aquarist went to Harvey Norman for his DSLR because they have a 24 month interest free installment plan. Not the cheapest, but the installment period was very attractive to him.
Alternatively, try www.clubsnap.com for used cameras. There are a lot of good condition cameras going for a song there too. In fact, I do recall seeing a few Canon 300D for sale. You'll save a few hundred easily.
Hope that helps and looking forward to seeing your pictures here soon!
Cheers,
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