Milling Machine Advice

[Washout]

Hi All,
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My router is running OK at the moment (shortly about to convert a rotary table and tail stock/chuck into a 4th axis), but I find myself looking to do some steel parts for various projects.
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What I am thinking of is a milling machine, which looking around for "bang for buck" is boiling down to these two:
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http://www.ebay.co.uk/itm/AMADEAL-AM...-/360422555676
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http://www.warco.co.uk/milling-machi...g-machine.html
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Both are roughly similar in travel, spindle HP etc. and both would be MT3 variants (I have a fair few MT2/3 bits from my lathe) but the Warco from the limited views looks to be a bit more sturdily constructed.
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Has anybody got experience of converting these to CNC and if I got another set of 3NM Nema 23 steppers, would they be up to the job or am I really looking at 34's? I can of course cut motor mounts etc. using my router and will probably use a box containing a pulley/belt for that purpose.
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Also I have seen various posts talking of epoxy/aggregate mix to essentially make a milling bed and I'm wondering whether this might be a cheaper alternative to a conversion - I'm thinking 3 slabs in essence with ground linear guides/rails; 1 for the base, 1 for the X and 1 for the Y - Z I haven't considered yet.
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In terms of timing its not urgent, so likely towards the back end of this year for either option, but obviously the conversion will be quicker in theory to complete.
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Opinions?
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Cheers
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Chris
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PS. I forgot to mention if I can get away with Nema 23's then I could use my existing control box - just swap the XLR connectors before using each machine (and make the necessary changes in MACH of course).