Using XMLStreamReader or Dom to Read SOAP Response from AS400

Example of XML Response: 

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Body>
        <PassThroughReqResponse xmlns="http://amsservices.com/">
            <PassThroughReqResult><?xml version="1.0"?>
<PickResponse>
  <Files>
    <File sagfile="WORK.7864470">
      <Item sagitem="WEBSERVICE.TAGS*WORK.7864470">
        <a1>POLICY.NUMBER</a1>
        <a2>CLIENT.CODE</a2>
        <a3>EFF.DATE</a3>
        <a4>EXP.DATE</a4>
        <a5>COV</a5>
        <a6>INS</a6>
        <a7>TERM</a7>
        <a8>POLICY.STATUS</a8>
        <a9>BILLING.METHOD</a9>
        <a10>31</a10>
        <a11>32</a11>
        <a12>33</a12>
        <a13>POLICY.STATUS</a13>
        <a14>NEW.REN</a14>
        <a15>CHG.TIME</a15>
      </Item>
    </File>
    <File sagfile="WORK.7864470">
      <Item sagitem="579615">
        <a1>TESTINGNEW</a1>
        <a2>ZIMJO1</a2>
        <a3>08/08/16</a3>
        <a4>08/08/17</a4>
        <a5>ARA</a5>
        <a6>CER</a6>
        <a7>A</a7>
        <a9>Agency Bill</a9>
        <a14>NEW</a14>
        <a15>12:06:46</a15>
      </Item>
    </File>
  </Files>
</PickResponse></PassThroughReqResult>
        </PassThroughReqResponse>
    </soap:Body>
</soap:Envelope>

//Capture SagittaID
        List<String> sagittaID = new List<String>();
        //List values to be returned 
        List<String> sagittaResponseTag = new List<String>(); 
        sagittaResponseTag.add('Item');
        sagittaResponseTag.add('a1'); //Client Code
        sagittaResponseTag.add('a2'); //Policy Number
        sagittaResponseTag.add('a3'); //Effective Date
        sagittaResponseTag.add('a4'); //Expiration Date
        sagittaResponseTag.add('a5'); //Cov
        sagittaResponseTag.add('a6'); //Insuror
        sagittaResponseTag.add('a7'); //Term
        sagittaResponseTag.add('a8'); //Policy Status
        sagittaResponseTag.add('a9'); //Billing Method
        sagittaResponseTag.add('a10'); //Written Prem
        sagittaResponseTag.add('a11'); //Written Agency Prem
        sagittaResponseTag.add('a12'); //Writer Producer Prem
        sagittaResponseTag.add('a13'); // Policy Status
        sagittaResponseTag.add('a14'); // New or Renewal
        for (Integer i = 0; i < sagittaResponseTag.size(); i ++) {  
            while (reader.hasNext()) { //while there are more XML events
                if (reader.getEventType() == XmlTag.START_ELEMENT) { //if this is the opening tag
                    String localName = reader.getlocalName();
                    String listTag   = string.valueOf(sagittaResponseTag.get(i));
                    System.debug('Inside Loop  :' + i + 'Local Tag Name  :' + localName + 'Does this equal :' + listTag);
                    if (sagittaResponseTag.get(i) == reader.getlocalName()) {
                        if (sagittaResponseTag.get(i) == 'Item' && reader.getLocalName() == 'Item') {
                            for (Integer a = 0; a < reader.getAttributeCount(); a ++) { 
                                if (reader.getAttributeLocalName(a).equals('sagitem')) { 
                                    theSagittaIdValue = reader.getAttributeValueAt(a); 
                                    sagittaID.add(theSagittaIdValue);
                                    System.debug('Found SagittaID: ' + i + '  Value :'+ theSagittaIdValue);
                                }  
                            } 
                        }  
                    } 
                } reader.next();  //advance to the next XML event
                if ('a1' == reader.getlocalName()) {
                    System.debug('Found A1');
                    while(reader.hasNext()) { //while there are more XML events
                        if (reader.getEventType() == XmlTag.END_ELEMENT) { //if this is the closing tag
                            break; //exist the loop
                        } else if (reader.getEventType() == XmlTag.CHARACTERS) { //if this is the content between the tags
                            theSagittaCodeValue = reader.getText();
                           // grab the content
                            if(theSagittaCodeValue != null) {
                                sagittaClientCode.add(theSagittaCodeValue);
                                System.debug('Sagitta Client Code: Insert' + ':' + theSagittaCodeValue );
                            }
                        }
                    }
                } reader.next(); //advance to the next XML event