Well malli lankabell shows 230k coz of that HUAWEI phone, its the connection between phone and the computer. Real connection speed around 153k, connect Suntel or SLT line with HUAWEI phone you can see 230k
Suntel 19.1kbps comes from that old fixed phone with big outdoor antenna. you can call them and upgrade to CDMA. Are you sure Suntel CDMA only has 115k? you on a HUAWEI device? Anyway as you mentioned its much more costly than Lankabell.
Dilaog GPRS is not even a comparable solution with CDMA. Its much more slower and will cost you like many times more.
I dont have ADSL yet

hope they will give it in March